Separate egg white and egg yolk. Save the egg yolk in fridge till needed.
Take a mixing bowl, add in flour, rye flour, salt, cocoa powder, caraway seeds, yeast and set aside.
Now in a jug, take water, brown sugar, olive oil, molasses, egg white and mix well.
Pour the wet ingredients into the flour mix and stir using a wooden spoon till combined.
Cover the bowl with a towel and set aside somewhere warm for at least 12 to 15 hours.
The dough will rise a bit.
Once the dough is risen, mix it gently till combined.
Grease a loaf pan, line with parchment paper and set aside.
Now spoon the batter into the loaf pan and set aside till it is risen a bit for 1 to 2 hours. If the weather is warm then it will rise faster. So keep an eye on it.
Meanwhile preheat oven to 180 degree C.
Now brush the top of the bread with egg yolk and sprinkle caraway seeds and sesame seeds.
Pop this into a preheated oven and bake for 40 to 45 mins.
Now remove it from oven and un mould the bread from the mould.
Pop it back into the oven, place it straight on the rack and bake for further 10 mins.
Remove from oven and cool it completely for atleast 3 hours.
Slice and serve.
Notes
Use a large mixing bowl to mix the dough. Since it will rise a bit in the 15 hours fermentation time.
Don't add too much yeast than recommended. Since the dough is fermenting for a long time, ¼ tsp is enough.
You can use ½ all purpose flour and ½ wheat flour instead of complete all purpose flour.
Use can use fennel seeds, nigella seeds as well.
Egg white is really important, so don't skip that.
For really black colour. you can add 1 tsp of activated charcoal.
STORAGE
Store black bread wrapped in plastic wrap at room temperature for 2 days.