Preheat oven to 350F (175C). Mix flour and baking powder and arrange on table/counter, create a well in the middle, add sugar, egg yolks, vanilla. Take a small amount of the flour and work it into the liquid mix. Add small pieces of cold butter and almonds. Using all the ingredients, create a smooth dough. If the dough is sticky, cool for a while. Form thumb sized rolls and cut into 2cm pieces. Roll out these pieces into 5cm long rolls which are slightly thinner at each end. Arrange as horns on a baking sheet. Bake at 350-380F (175-195C) for about 10 minutes. Decorate with icing sugar.