With an electric mixer, beat the 1/2 cup butter and the cream cheese until smooth. Add the flour and beat until fully combined. Cover the bowl with plastic wrap and chill in the refrigerator for 1 hour.

Preheat the oven to 325 degrees F. Spray a 24-cup mini-muffin pan with cooking spray.

In a large mixing bowl, whisk together the melted butter, egg, brown sugar, vanilla and salt until smooth. Set aside.

Shape the chilled dough into 24 balls, about 1 inch in diameter. Press each ball into a cup of the muffin pan, spreading evenly and up the sides, then spoon 1 teaspoon of the pecans into each muffin cup. Fill each cup with the egg mixture until evenly distributed, about 1 teaspoon in each. Bake until the filling is set, about 25 minutes. Cool on a wire rack for 10 minutes, and then remove from the muffin pan.