Icelandic Thunder Bread

Icelandic Thunder Bread
Sally Williams Photography/Photo Library/Getty Images
Prep: 20 mins
Cook: 4 hrs
Total: 4 hrs 20 mins
Servings: 12 servings
Nutritional Guidelines (per serving)
120 Calories
3g Fat
22g Carbs
2g Protein
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Nutrition Facts
Servings: 12
Amount per serving
Calories 120
% Daily Value*
Total Fat 3g 4%
Saturated Fat 1g 4%
Cholesterol 2mg 1%
Sodium 370mg 16%
Total Carbohydrate 22g 8%
Dietary Fiber 1g 4%
Protein 2g
Calcium 137mg 11%
*The % Daily Value (DV) tells you how much a nutrient in a food serving contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
(Nutrition information is calculated using an ingredient database and should be considered an estimate.)

This moist, Icelandic dark rye bread (rugbrauð), also called "thunder bread" or "pot bread," has many similarities to Boston brown bread—it is leavened with baking powder, not yeast, and molasses give it color and a hint of sweetness. Traditionally, Icelandic rye bread is prepared over the course of 12 or more hours by placing the dough into covered pots and sinking these into geothermal springs. If you do not have a geothermal spring handy, it can be prepared in tin cans or ramekins tented with aluminum foil and steamed in a slow cooker. Steaming the bread is the key.

What is the origin of the name “thunder bread”? Sources say the moniker comes from the after-effects of eating too much of this high-fiber rye. Also, it is served at Thorrablot, the Viking festival in honor of Thor, the god of thunder.


  • 2 1/2 cups rye flour
  • 1 1/2 cups all-purpose flour
  • 1 heaping tablespoon baking powder
  • 1/2 teaspoon salt
  • 1/2 cup brown sugar (packed)
  • 1 cup milk (scalded and slightly cooled until lukewarm)
  • 1 tablespoon molasses
  • 2 cups hot water

Steps to Make It

  1. Gather the ingredients.

  2. Whisk together the rye flour, all-purpose flour, baking powder and salt in a large bowl or the bowl of a stand mixer.

  3. Mix in the brown sugar.

  4. Stir the molasses into the lukewarm milk that has been scalded until it dissolves.

  5. Then slowly stir milk into the dry ingredients (the dough hook of a mixer works great for this).

  6. Knead the dough until it is shiny and all the flour is incorporated. Divide into two portions.

  7. Butter the insides of two tin cans (at least 19 ounces each–watch out for sharp edges) or two ceramic bowls or ramekins, each one large enough to hold 1 1/2 cups of batter.

  8. Tent the molds with aluminum foil, leaving about an inch of airspace for the bread to rise as it cooks. Secure the edges of the foil tightly around the rims of the molds with twine or rubber bands.

  9. Place the molds in your slow cooker (rest cans, if using, on a trivet or canning jar lid inside the cooker to help the steam circulate). Pour in enough hot water into the slow cooker to cover the lower half of the molds (about 2 cups).

  10. Put the lid on the cooker and raise heat to high. Allow it to simmer for 4 hours, checking occasionally to ensure that the water hasn't boiled out.

  11. Remove bread and serve immediately with butter, cold pickled herring, lamb pate, cold meats, or cheese.

  12. Enjoy!


Important: The dough will rise while cooking, so whichever molds you use should only be filled 2/3 below the top edge.