Cream together sugar and butter. Beat in egg yolks, almond and vanilla extract.
Add flour, baking soda, and cream of tartar. Stir. The dough will be more firm than typical cookie dough.
Roll dough into walnut-sized balls and place 2 inches apart on cookie sheet. Don't flatten! Bake 10 to 11 minutes, until tops are cracked and just turning color.
Frosting
In a large bowl, cream together the confectioners' sugar and butter until smooth. Gradually mix in the milk, almond and vanilla with an electric mixer until smooth and stiff, about 5 minutes. Color with food coloring if desired.