Beat butter and cream cheese until creamy. Mix in flour on low until a soft dough forms. Shape into a disk, wrap, and chill at least 1 hour.
Heat oven to 350°F (175°C). Spray a mini muffin tin well. Divide dough into 24 pieces and press into the cups.
Whisk brown sugar, egg, melted butter, vanilla and salt until smooth.
Put chopped pecans in each shell, then top with filling, filling only two-thirds full.
Press a pecan half on top of each. Bake 18–20 minutes until golden and filling is set.
Cool completely in the pan before removing with a small knife.