In a medium bowl, combine butter and cream cheese until smooth.
Stir in salt, Parmesan cheese and flour until blended.
Shape into a ball; wrap in waxed paper or foil.
Refrigerate 1 hour.
Preheat oven to 425°F (220°C).
Roll out dough on a lightly floured surface to about 1/8-inch thickness.
Cut into 3-1/2-inch circles.
Press over bottoms and up sides of 2-inch tart pans or muffin cups.
Bake for 5 to 7 minutes in preheated oven until golden brown.