1Heat oven to 350°F. Place paper baking cup in each of 24 regular-size muffin cups. Make brownie batter as directed. Fill each baking cup with about 2 level measuring tablespoonfuls of batter.
2Bake 18 to 22 minutes or until toothpick inserted in center comes out almost clean. Do not overbake. Cool in pan 20 minutes. Carefully remove paper baking cups from muffins; cool upside down about 15 minutes or until completely cool.
3Cut small heart out of paper. Place on bottom of cupcake. Sprinkle with powdered sugar. Carefully remove heart. Repeat with remaining cupcakes.