Mix flour, baking powder, salt and sugar in a bowl, work in butter with a fork until small crumbs are formed. Whisk the sour cream with vinegar and mix in quickly with a fork until a ball of dough is formed.
Flatten the dough by hand on the floured work surface, about two centimeters thick. Cut out round shapes with a glass. Brush with egg and bake for about 10 to 15 minutes until light brown.
For an extensive breakfast or brunch. Delicious and classic with strawberry jam and salted butter. Scones (and biscuits) taste best super fresh - otherwise warm them up briefly in the oven.