Allow the butter to reach room temperature. Put it in a larger bowl, add a half cup of sugar and incorporate it with a fork or spoon. It is not necessary to dissolve the sugar in butter, just mix well.

Put the baking powder in the flour, mix them and add over the butter.

With your hands, incorporate the flour into the butter, until it crumbles.

Put the egg yolks and sour cream over the cheese - mix well.

Separately, beat (with the mixer) the egg whites well with half a cup of sugar, until they increase in volume 3 times and make a hard foam and add them over the cheese mix.

Gently mix the composition (from top to bottom) so that no air comes out of the egg whites.

In a deeper baking tray, evenly place 2/3 of the dough crumbs.

Place the cheese composition over the crumbs and cover with the rest of the crumbs.

Put the tray in the oven and let it brown over medium heat.

When ready, allow to cool and cut squares, triangles, etc.

Good appetite!