For dough: Put the flour and salt in mixing bowl; stir to blend. Scatter the butter slices over the flour and cut in with a pastry blender until the mixture consists of particles the size of small peas to bread crumbs.

Stir in the sour cream with a fork. The pastry will appear dry, because the sour cream is thick and doesn't disperse easily. With your hands make the dough into a ball.

Divide in 3 equal parts.  Shape each piece into a 5" square about 5/8" thick. Wrap in plastic and refrigerate until cold and firm, at least 4 hours and up to 3 days; or freeze, well wrapped, up to 1 month.

Cream Cheese Filling:  Process all the filling ingredients in a food processor bowl until the mixture is smooth.

Remove one pastry square from refrigerator. Set aside for 10 minutes before rolling it. On a floured surface, roll the pastry into a rectangle slightly less than 1/8" thick. With a ruler and a pastry wheel, trim the ragged edges; then measure and cut the pastry into 3" squares.

Lay the pastry squares across the top of ungreased 12-cup miniature muffin pans, centering each square over one cup. Spoon 1 heaping teaspoon of filling on each square; then bring opposite corners to the center and press lightly to seal. This process will also ease the pastry into the cup. Refrigerate for at least 30 minutes. Roll and shape the remaining pastry squares in the same fashion.

Adjust rack to lower third of oven; preheat oven to 375°. Bake two to three pans at a time for about 20-25 minutes or until the pastries are light brown. Remove pan from oven to a wire rack for about 10 minutes. Remove pastries from pan to wire rack to cool completely.

Sprinkle with powdered sugar before serving at room temperature.

Note: if not serving the same day baked, stack undecorated pastries in airtight sturdy plastic containers and freeze up to 2 weeks. To serve reheat to freshen in a 325° oven for about 7-12 minutes or until warm; cool slightly, then sprinkle with the powdered sugar.