The evening before, put all the ingredients for the sourdough into a 720 ml jar, stir well, should become a thick mush, close the lid, put it in a room-warm cupboard in the dark.
In the morning:
Stir the sourdough and put it in a mixing bowl, rinse the glass with a little seltzer, add 400 ml of carbonated mineral water, stir gently, pour in the mixed dry ingredients and stir everything for 4-6 minutes on medium setting.
In the meantime, grease the muffle wells in the trays well, also coated, fill about 2 tablespoons of dough in each well, let rise for a few hours at a warm room temperature, or in the oven, top + bottom heat at 30 ° C (lights on and on a little more) until the dough has clearly lifted.
Bake in the cold oven at approx. 140 ° C for approx. 35-45 minutes. Needle test, but you can also see it.
Leave in the mold for a few minutes, put a board on top of the muffins, turn everything over, remove the baking sheet, if you let them slip out, you can break them, let them cool before cutting, a saw knife is an advantage.