THAW pastry sheet at room temperature 30 min. Preheat oven to 375°F.
MIX sugar, cornstarch and coffee crystals in saucepan. Stir in
milk. Cook and stir over medium heat until mixture boils and thickens. Remove from heat and gradually stir half of hot mixture into eggs. Return egg mixture to saucepan. Cook and stir over medium heat 1 min. Remove from heat. Sprinkle
gelatin over water and let stand 1 min. Stir into pastry cream. Stir in butter. Place plastic wrap directly onto surface of pastry cream and refrigerate 30 min.
UNFOLD pastry sheet on lightly floured surface. Roll into 12" square. Cut
into 4 (12"x3") rectangles. Cut 3 rectangles into 4 squares, making 12 squares in all. Cut remaining rectangle into 12 (2"x1 1/2") rectangles. Pierce pastry squares with fork. Place on baking sheet.
BAKE 15 min. or until golden
brown. Remove from baking sheets and cool on wire racks.
FOLD pastry cream into whipped cream. Cover and refrigerate mousse 15 min. or until mixture holds its shape.
DIVIDE mousse among large pastry squares. Top
with small pastry squares and sprinkle with confectioners' sugar.