Spray a 24 indentation muffin tin with cooking spray.
Prepare crust first. Beat butter and cream cheese at medium speed with an electric mixer until creamy. Add flour to butter mixture and stir until incorporated. Shape mixture into 24 neat balls; cover and chill 1 hour. (I set the balls in mini muffin tin and put the pan in the refrigerator). Press balls into discs and fit them neatly into the 24 indentation mini muffin tin; dough should come all the way up the sides.
Filling: Toast the pecans using your favorite method (350 for 8 -10 minutes). Let them cool and then chop. Sprinkle chopped pecans in the pastry lined cups, dividing evenly among them.
Stir together egg, brown sugar, butter, vanilla and salt. Spoon filling over pecans. Top each with a pecan half. Bake at 325 degrees F. for 25 minutes.
Remove from oven. While tassies are warm, slide a knife around edge and lift tassies from pan.