Recipe courtesy of Mavis Ceci 

INGREDIENTS
Dough
1 cup margarine, softened 
1-1/2 cups flour
1/2 cup sour cream

Filling
1 cup shortening 
1 cup margarine
2 cups sugar 
2 egg whites (pasteurized eggs suggested) 
4 teaspoons vanilla 
1 cup hot milk
powdered sugar for dusting

DIRECTIONS
Combine the ingredients for the dough by hand until the mixture forms a sticky ball. Cover with plastic wrap and refrigerate overnight.

Preheat the oven to 425 degrees. Divide the dough in half. Roll one half out on a floured surface to form a (roughly) 10-inch square. Cut dough into one-inch-wide strips and wrap on forms (old-fashioned wooden clothespins or wooden or metal dowels). Bake for 11 minutes, or until lightly browned. Cool completely.

To prepare the filling, beat shortening, margarine and sugar together. Beat in egg whites. Add vanilla and milk a little at a time until thoroughly combined. Using a pastry bag, pipe the filling into cookies. Sprinkle with powdered sugar.