Not too sweet, sourdough doughnuts are cake-like and dense thanks to the inclusion of buckwheat flour. Filling with a wholesome rustic texture and flavor, these doughnuts are leavened first through the same method used to prepare sourdough bread.
Stir one cup proofed sourdough starter with one-half cup milk kefir, two and one-half cups white wheat flour and a half cup buckwheat flour until it forms a ball. Allow the dough to ferment at room temperature overnight or up to twelve hours. Punch down the dough, flour your hands and working surface then knead in one-half cup butter. Allow the dough to rise again until doubled in bulk. Roll out the dough on a floured work surface until it’s about one-half to three-quarters of an inch thick, then cut out the doughnuts.
Heat enough coconut oil, lard or tallow in a cast-iron skillet to fill it by one-inch.
While the fat is heating, prepare the cinnamon-sugar topping by pouring one-half cup unrefined cane sugar and one-quarter cup ground cinnamon in the basin of food processor. Process the cinnamon and sugar until it forms a fine powder, then pour the powdered cinnamon-sugar into a wide bowl and set it aside until the doughnuts are finished frying.
When the fat has reached about 350 degrees Fahrenheit, place doughnuts into the skillet – without overcrowding – and fry them about one to two minutes on each side. Remove the doughnuts from the skillet and allow them to cool slightly before rolling them in powdered cinnamon-sugar.