Beat egg until light and frothy. Add milk, lard, and butter; beat well.
Combine flour, baking powder, and salt in a medium mixing bowl; stir well. Gradually add egg mixture, beating well. Chill dough at least 2 hours.
Roll dough to 1/8-inch thickness; cut with a 1 1/2-inch biscuit cutter. Place on ungreased baking sheets. Brush tops with egg white, and sprinkle with sesame seeds. Bake at 400° for 10 to 12 minutes.