Add cold butter grated on a coarse grater to half of the flour (you can freeze it in the freezer).
Rub your hands into crumbs.
In a separate bowl, whisk together the egg, sugar, salt and kefir.
Add the liquid mixture to the butter crumbs and mix well.
Add the remaining flour mixed with baking powder.
Knead a soft dough.
Divide the dough into 4 parts.
Roll out each part of the dough into a 3 mm thick layer.
Sprinkle 1/2 tablespoon of starch.
Brush with 2 tablespoons of jam.
Sprinkle with chopped nuts.
Fold in 3 turns. Pinch the edges well.
Place on a baking sheet lined with parchment seam down. Flatten a little by pressing from above.
Bake at 180 degrees for 30 minutes until lightly browned.