Shred cabbage and mix with 1tablespoon salt. Let it stand for at least 1 hour. Squeeze it dry.
Melt 2tablespoons of the butter in a frying pan and add the sugar. Brown it carefully; don’t let it burn. Add the cabbage and wilt over very low heat for about 30 minutes, or until brownish and cooked. Add the pepper and mix. Remove cabbage from the frying pan and set aside to cool.
With a pastry blender mix remaining 8tablespoons butter, the flour and baking powder until the mixture forms crumbs. Add egg yolk, ½teaspoon salt and the sour cream. Knead it quickly, to make a dough. Wrap in wax paper and put in the refrigerator for 30 minutes.
Remove dough from refrigerator and mix in the cold cabbage mixture. Put it back into wax paper and refrigerate for another 30 minutes. Preheat oven to 375°F.
Remove dough from refrigerator and roll between sheets of wax paper to ½-inch thickness.
With a 1-inch biscuit cutter, cut out biscuits. Place them on a baking sheet.
Score them with a knife. Beat the whole egg with 1teaspoon water, and brush this glaze over the biscuits.
Bake in the preheated oven for about 30 minutes, or until golden.