For pastry:Using electric mixer, cream butter and cream cheese together.Add flour and beat just until dough comes together; do not overmix.Wrap in plastic wrap and chill until firm, at least 2 hours.
For filling:Blend sugar, egg, butter, bourbon, vanilla, and salt.
To assemble:Preheat oven to 350 degrees.Lightly butter 24 miniature tartlet pans or muffin cups.Roll dough out on lightly floured surface to thickness of 1/8".Cut out 24 rounds, using 2-1/4" cutter.Reroll scraps as necessary.Fit rounds into prepared pans or cups; trim edges.Divide pecans among tartlets.Pour in filling.Bake until filling has set and cracked slightly, 25-30 minutes.Cool in pans on rack.