Preheat oven to 350° F. Beat butter until creamy; beat in sweetened condensed milk and egg yolks. Sift flour, baking powder, cinnamon and ginger; beat into butter mixture until you get a smooth paste. Wrap in plastic wrap and refrigerate for 15 minutes. Roll dough out on a floured surface; cut dough into shapes with cookie cutters. Place on baking sheet. Bake for 15 to 20 minutes.