Preheat the oven to 350°F. Lightly grease a 24-cup mini muffin pan.
Beat softened butter and cream cheese until smooth and fluffy.
Mix in the flour and a small pinch of the salt until a soft dough forms.
Chill the dough 10 minutes, then divide into 24 pieces. Roll into balls and press into cups to form shells.
Whisk the egg, brown sugar, melted butter, vanilla, and remaining salt until glossy. Fold in pecans.
Spoon the filling into shells, about 1 tablespoon each, leaving a little space at the top.
Bake 20–22 minutes, until centers are set and edges are golden. Cool 10 minutes, then loosen and transfer to a rack.