1Heat oven to 350°F. Line 12 mini and 12 regular-size muffin cups with paper baking cups. In large bowl, using whisk, mix flour, granulated sugar, 1/2 cup cocoa, the baking soda and salt. In medium bowl, using whisk, mix soymilk, canola oil, vinegar and 1 1/2 teaspoons vanilla. Pour wet mixture into dry mixture; beat with whisk until well mixed. Stir in chocolate chips. Fill each mini muffin cup with 1 level measuring tablespoon batter. Divide remaining batter among regular-size muffin cups.
2Bake mini cupcakes 12 to 16 minutes or until toothpick inserted in center comes out clean. Bake regular-size cupcakes 22 to 26 minutes or until toothpick inserted in center comes out clean. Cool in pans 10 minutes; remove from pans to cooling rack. Cool completely, about 30 minutes.
3For frosting, in large bowl, beat margarine, coconut oil, 1 teaspoon vanilla and 2 teaspoons of the water with electric mixer on low speed until smooth. Beat in 3 tablespoons cocoa and the powdered sugar, 1 cup at a time. Gradually beat in just enough remaining water until smooth and spreadable.
4To assemble cupcake stacks, remove paper baking cups. Pipe frosting on top of 1 regular-size cupcake. Top with 1 mini cupcake; frost top of mini cupcake. Repeat with remaining cupcakes and frosting. Garnish with chocolate curls and coconut, if desired.