Heat oven to 350°F for shiny metal pans (or 325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups.
In large bowl, beat cake ingredients with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally. Divide batter evenly among muffin cups.
Bake 18 to 23 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove from pan to cooling rack. Cool completely, about 1 hour.
In medium microwavable bowl, microwave baking chips on High 30 seconds; stir until melted. If necessary, microwave 15 seconds longer. Stir until smooth; cool 5 minutes. Stir in frosting until well blended.
Immediately spread or pipe frosting mixture on cupcakes. Sprinkle with cinnamon. Store loosely covered at room temperature.
High Altitude (3500-6500 ft): Decrease water to 1 1/4 cups.