THAW pastry sheet at room temperature 40 min. Preheat oven to 400 degrees F. Mix brown sugar, butter and pecans.
UNFOLD pastry on lightly floured surface. Roll into 15"x 12" rectangle. Cut into 20 (3") squares. Press squares into bottoms of 3" muffin-pan cups. Place 1 heaping tsp. pecan mixture in center of each.
BAKE 12 min. or until golden. Remove from pans. Let cool. Sprinkle with confectioners' sugar. Makes 20 pastries.