Dough: Cream together butter, cream cheese and sugar. Add flour. Beat into smooth dough. Divide dough into 24 equal balls. Press into individual mini muffin tins. Smooth evenly on bottom and up sides.
Sponge: Cream together sugar, lemon, yolk. Add butter, salt, flour and milk.
In a separate bowl, eat egg white into stiff peaks. Fold beaten whites into batter. Spoon batter into prepared dough cups. Bake at 350 for approximately 25 minutes until cookie browns and inserted toothpick comes out clean.