Start with mixing first 3 ingredients and let it stand for several minutes to foam.
Add the rest of water, coffee powder, cocoa and molasses. Add rye flour and stir until there are no lumps.
Now add salt and 1AP and 1WW flour. Start kneading and adding some more WW flour, as much as is needed to make slightly sticky dough. Place the dough in a big bowl, cover with plastic and let it rise for 1 hour.
Punch the dough down and press with your hands to create square disk. Cut it into smaller squares (I made 19 actually), transfer these buns onto lined with paper baking sheet and let them rise again, 45 minutes approximately.
Preheat oven to 190C. Coat each with egg white wash and sprinkle with flax seeds.
Bake for 20 minutes and let them cool on a wire rack.