1. In the bowl of a mixer or food processor, combine butter and cream cheese, mixing well.
2. Add flour and sugar and mix well.
3. Wrap in wax paper and refrigerate for at least 4 hours or overnight.
4. Roll dough to ¼" thickness and cut into 3 to 4 inch round circles and place 2 inches apart onto the prepared cookie sheets.
5. Place a teaspoon of filling into the center of each cookie and pinch the sides to form three corners. Moisten with water if necessary.
6. Bake at 375° degrees for 6 to 8 minutes in the preheated oven, or until lightly browned.
7. Allow cookies to cool for 1 minute on the cookie sheets before removing to wire racks to cool completely.