1. Preheat the oven to 325°. In a standing mixer with a paddle attachment, mix the butter and cream cheese until fluffy, about 3 minutes. Add the flour and mix just to combine. Divide the dough into 24 balls and place one ball in each cup of a small muffin tin. Push the dough up the sides of each depression, creating a well in the center of the dough.

2. Make the filling: Place a small amount of the pecans in the cups of dough, making sure to completely fill the cups. In a small bowl, whisk together the butter, brown sugar, salt, egg and vanilla.

3. Pour the filling over the pecans, making sure not to overfill the tassies. Place the tin in the oven and bake until the dough is light brown and the filling is slightly cracked on top, about 15 minutes. Carefully remove the tassies from the hot muffin pan immediately and serve warm, or let cool on a rack until the cookies are room temperature.