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Thunder Bread Recipe – A Geothermal Bake Off in Iceland

Making Thunder Bread in Iceland

There’s a rye bread that’s been baked underground in geothermal springs in Iceland for generations. The Icelandic bread is dark, dense, deliciously sweet and it’s called Hverabrauð, Thunder Bread or Icelandic rye bread. Read on to find out about our day in Iceland and for the thunder bread recipe which I recommend you have a go at making at home (you don’t actually need a thermal lake in your garden to do this).

I went on a whirlwind, 24-hour visit, to Iceland to discover how Thunder Bread is made and to catch a behind-the-scenes glimpse of the Celebrity Cruises and Waitrose ‘Taste of Travel’ food and travel series. The series is filmed with the lovely Rosie’s Deli Cafe owner and presenter Rosie Lovell.

A day in Iceland and a Thunder Bread recipe

On the road in Iceland

On the road in Iceland

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On the Road in Iceland

We set out from Reykjavik at early doors, driving through some stunning Icelandic scenery on our journey. We had a very quick stop at Þingvellir (pronounced Thingvellir) National Park, home to the world’s oldest parliament, where we were able to check out the amazing views.

We walked through one of the fault lines where the earth’s tectonic plates of the Mid-Atlantic Ridge have shifted. It was good to see the Icelandic scenery in the summer. The last time I stood here during our Golden Circle Tour and looked at this view it was early February with a very wintery looking scene and a vicious wind.

Get a taste for Iceland in an Icelandic Food Tour – check rates and availability

Þingvellir (Thingvellir) National Park

Þingvellir (Thingvellir) National Park

Laugarvatn Fontana

We arrived at Laugarvatn Fontana and met Sigurdur Hilmarsson (Siggi), manager and chef. Siggi would be teaching Rosie how to make Icelandic Thunder Bread from a recipe handed down by his grandmother.

Laugarvatn Fontana is a geothermal spa with pools, saunas and a restaurant with a strong Icelandic design vibe. It sits on the edge of Lake Laugarvatn which laps onto a black volcanic shoreline and has three geothermal springs. The springs provide energy for the entire village and the spring at Fontana is used for cooking the Thunder Bread.

Read more: Tips for Visiting Reykjavik | What to Eat & Drink in Iceland | Touring Iceland’s Golden Circle

Laugarvatn Lake, Iceland

Laugarvatn Lake, Iceland

What is Thunder Bread

Thunder Bread is just a nickname, it’s actually called Hverabrauð (hot-spring bread), or rugbrauð and is a type of rye bread. It’s steam-cooked underground in a geothermal spring. Every Icelandic family’s recipe for Thunder Bread is slightly different with ‘more of this’ and ‘less of that’. Of course, each family thinks theirs is the best.

Thunder Bread is a year-round essential food in Iceland, eaten with smoked trout, salmon, herring or just plain butter.

It is also served at Thorrablot, the Viking festival honouring Thor, the god of thunder. As Siggi says ‘It’s pure Iceland’.

making the thunder bread recipe

Rosie and Siggi making thunder bread

Recipe for Thunder Bread

Icelandic Thunder bread, rye, rugbrauð
Yield: 1 loaf

Icelandic Bread - Thunder Bread recipe

Prep Time: 15 minutes
Cook Time: 5 hours
Total Time: 5 hours 15 minutes

A recipe for Icelandic Thunder Bread also known as Rye Bread


  • 320g rye flour
  • 85g all purpose flour
  • 200g sugar
  • 8g baking power
  • 1g salt
  • 500ml milk


    Mix together all the dry ingredients in a medium bowl. Add the milk and mix together. The dough will be very wet.

    Grease a metal pot (with a lid) so the bread won’t stick when it’s cooked. 

    If, like me, you don't have a geothermal spring in your garden(!) Siggi suggests you bake in the oven at 120 degrees Celsius (with the lid on) for five and a half hours, or until bread is cooked in the middle.

    Alternatively you could simmer in a slow cooker or crock pot around 4 hours. The bread will steam if cooking this way and you'll need to add water to the crock pot and check regularly to ensure it doesn't boil dry.

    Split the dough into two and place in two medium ceramic bowls or tin cans, ramekins could also be used.  Whichever you use, tent with aluminum foil to steam the bread. 


To convert to cups measurement use this converter.

Nutrition Information



Serving Size


Amount Per Serving Calories 246Total Fat 2gSaturated Fat 1gTrans Fat 0gUnsaturated Fat 1gCholesterol 4mgSodium 64mgCarbohydrates 53gFiber 4gSugar 23gProtein 6g

Nutritional information is estimated.

If rye flour isn’t available in your local supermarket you can buy it here.

Burying the Thunder Bread

We went outside to the lakeside to watch Siggi bury the bread in the geothermal spring. We could see steaming bubbles exploding in the black volcanic sand by the water’s edge and smell the faint, eggy smell of sulphur in the air.

First, Siggi dug up the previous day’s thunder bread and cooled off the hot pot in the lake. Next, he buried the freshly made pots of thunder dough in the geothermal spring.

Burying Thunder Bread

Burying Thunder Bread

The thunder bread is taken out of its pot and neatly sliced ready to eat…

Thunder bread with Rosie and Siggi

Thunder bread with Rosie and Siggi

What does Thunder Bread Taste Like?

The Thunder Bread was delicious! It was very dense and almost cake-like. I ate it, still warm, without any topping – it was moist and had a faint caramel-like taste. Really yummy. If I had a thermal spring in our garden at home I’d be baking it regularly!

Icelandic Thunder bread

Icelandic Thunder bread

Why is Hverabrauð called Thunder Bread?

Apparently if you eat too much Hverabrauð you’ll experience a ‘gas situation’! Since we were getting on a flight that afternoon I only had two slices so can’t confirm whether this is farty fact or farty fiction.

Filming with Rosie

It was fascinating to be part of a film shoot and see the painstaking procedure that goes into making just a short 2-3 minute film. The crew, Rosie and Siggi patiently filmed over and over until the producer was happy with the footage and sound.

I can’t even imagine the amount of work that goes into editing everything to produce the final film. The crew have worked on a number of ‘A Taste of Travel’ videos with the Celebrity Cruises and Waitrose partnership. ‘How to make ‘Manti’ in Istanbul and what goes into producing the best gelato in Florence.

Thunder bread going into the spring

Filming in Iceland

Rosie Lovell

We had a chance to have a quick chat with Rosie Lovell, cookery writer, cafe/deli owner and presenter before filming started.  After leaving university, Rosie went to Glastonbury, came home and straight away opened Rosie’s Deli Café in Brixton – she’s never looked back. She recently opened a second Deli Cafe in Peckham – ‘I’ll only in open in places I love, she says – I’m too emotional!’ She’s very hands-on and splits her time between the two cafes cooking up breakfasts, brunches, sandwiches and cakes.

Rosie’s written two cookery books which, she says, charter her age. Her first book, Spooning with Rosie, has simple, student, comfort food. The second, Supper with Rosie, is a bit more grown up. When asked about her food/travel wishlist there was barely a hesitation. ‘Tokyo because it’s so immersive and different; overwhelming, exciting and fundamentally foreign.’

So where does Rosie head when she’s going out for a meal? Now that we have a son it’s more neighbourhood – easy, seasonal, accessible and appealing. All I want is ‘a really flipping nice supper!’ I couldn’t agree more.

Have you come across any unusual foods on your travels – tell all, what and where in the comments below. Let me know if you bake this thunder bread recipe and what you think of the result.

Many thanks to Celebrity Cruises for inviting me along to this big Icelandic bake off!

Pin it for later!

Sliced Thunder Bread on wooden board with knife

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Sunday 20th of February 2022

Would like to try in my crockpot? Anyone done this? Thanks


Thursday 19th of May 2022

I am also waiting for someone to answer this question, please.

David E

Saturday 5th of February 2022

Can’t wait to try making this at home. We were there on Dec 18, 2021 and loved the bread. Warm with butter and the smoked trout was the best nom noms the whole trip. The meat soup in Vik was right up there, too!

Suzanne Jones

Monday 7th of February 2022

Sounds like you had a great trip. The bread is so good, let me know how you get on making it at home

Tim H

Monday 11th of January 2021

We went to La Fontana in 2016, but couldn't afford the prices. However, I baked the bread last night (10 hours) in a slow gas oven (100°C) and it's delicious for breakfast. It tastes better with savoury than with sweet things, and absolutely fabulous with ample amounts of salted butter. I cut back on the amount of sugar and used 125g Golden Syrup instead. I also used kefir instead of milk, and 2 tsp bicarbonate of soda instead as I didn't have enough baking powder; the colour is like chocolate cake! White rye flour does the trick very well, but I'll try a 50/50 mix wholemeal rye and white rye next time. Maybe some caraway as well...? Thx for sharing the recipe.

Suzanne Jones

Monday 11th of January 2021

The thought of it with salted butter is making my mouth water. I agree it's better with savoury too. It's a while since I've made it but you've inspired me to bake it again - it'll make a change from sourdough. Thank you for sharing your tips and swaps. The caraway is inspired :)

Beth East

Tuesday 22nd of December 2020

Went to La Fontana and had the amazing bread there. I lost my recipe, so was glad to see you posted. I converted everything, including the oven temp. Bread was done in just over 2 hours in my Staub Dutch oven. The bottom was a tiny bit overdone, but it was delicious, fresh out of the oven with Irish butter! I'm thinking I might lower the temp next time. Overall, it was great and brought back lovely memories of Iceland!

Suzanne Jones

Tuesday 22nd of December 2020

Hi Beth, I'm glad you found the recipe useful. The thunder bread sounds divine with Irish butter. I'll try the recipe again and test with a lower temperature and let you know the outcome. Thank you for letting me know

Henri Levison

Wednesday 29th of July 2020

Very easy and result with a great taste ! Only prepared in a normal oven.

Suzanne Jones

Wednesday 29th of July 2020

The flavour's very different to any other bread - glad you enjoyed it :)

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