In a bowl, mix the egg with salt and sugar, add the slaked baking soda and sour cream, and stir again with a fork.

Sift in the flour in parts and knead the dough, gathering it into a ball.

Divide the dough into 85-gram pieces. Roll each ball into a rope - the ends should be thinner than the middle - and twist into a kalach.

Place the rolls on a parchment-lined baking sheet and brush with the egg yolk and milk.

Bake in an oven preheated to 185 °C for 25-30 minutes.