For the dough: In a large bowl, beat butter and cream cheese until light and fluffy. Gradually add the flour, mixing until the mixture forms a ball. Cover and refrigerate for 30 minutes.
For the Filling: Mix brown sugar, egg, melted butter, and vanilla extract in a large bowl until combined. Then, stir in the pecans. Set aside.
After chilling the dough, roll it into one inch balls. Press into the bottom and up the sides of greased mini muffin cups/tin. Next, spoon the filling into each of the cups, filling about 3/4 full.
Bake at 350 degrees F for 20-25 minutes. Cool 2-3 minutes before removing from the pans.