Mix soft butter with powdered sugar, add protein, vanilla and mix again. Pour in flour and knead not too thick dough.
Mix jam with starch.
Transfer the dough into a pastry bag, squeeze cookies onto a baking sheet covered with parchment in the form of a ring with a recess.
Put the filling in the recess on each cookie. Bake at 200 degrees for 10-15 minutes.
Cool and serve a little.