Preheat your oven to 125 F(50C). Warm 4 cups (1 liter) of water in a large oven-safe pot to 140-158 F (60-70C). Simmering, not boiling. Add 1 cup malted rye and 1,8 cups rye flour to the water and mix into an even porridge consistency. Sprinkle some rye flour on top and lift the pot in the oven for 1½-2 hours.
Warm 4 cups of water so it simmers.(same temperature as above) Add the water and 1 cup malted rye +1,8 cups rye flour to the mixture. Sprinkle some rye flour on top. Let it stand in the warm oven for another 1½-2 hours.
Repeat the previous step and add the rest of the malted rye and rye flour.
Lift your pot from the oven and add 1 cup of water, the dark syrup, salt, bitter orange peel and grated orange zest. It should be loose in consistency.
Boil the rye porridge on the stovetop for 10 minutes while stirring at the same time. Let it cool before baking in the oven. You can, for example, let it stand overnight in the fridge.
Preheat the oven to 320 F (160°C). Add rye porridge into your paper loaf tins so they are half full. Add some syrup-water mixture on top. Bake for about 2,5 hours. Let mämmi cool down before eating it with heavy cream and sprinkled sugar on top.