In a mixing bowl (or food processor), whisk together flour, powdered sugar, cocoa and salt. Add cold, grated butter, and mix with beaters (or food processor) until mixture looks like pebbly sand. Add egg and ice water (1 tablespoon at a time), and mix on low speed just until it begins to form clumps. Use hands to form into a ball, handling only as much as necessary, then flatten slightly.

Dust work surface and top of dough with cocoa, and gently roll pastry to about 1/8 inch thickness, turning often and dusting with more cocoa as needed.

Cut 3 ½ inch circles (or circles slightly larger than muffin tin openings), and using a spatula, gently transfer them to muffin tin, pressing into corners to form shells.

Cover and chill 2 hours or overnight. DO NOT skip the chilling!

Preheat oven to 350 degrees F.

Prick bottoms of shells a few times with a fork. Place cupcake liners into pastry, and fill with rice or pie weights. Bake 15 minutes. Remove cupcake liners, and bake another 2-3 minutes. Allow to cool in pan 2-3 minutes, and then carefully remove and transfer to wire rack to cool completely.