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1
To make the cupcakes: Preheat oven to 325 degrees.
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Line 36 (2 1/2 inch) muffin pans cups with paper liners.
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3
In a medium bowl, whisk together cocoa powder, food coloring and boiling water.
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Set aside to cool.
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5
In a bowl of an electric mixer fitted with a paddle attachment, cream butter and shortening until smooth.
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Scrape down bowl and add sugar.
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Beat until mixture is light and fluffy, about 5 minutes.
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Add eggs, one at a time, beating well after each addition.
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Stir buttermilk and vanilla into the cooled cocoa mixture.
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Sift cake flour and salt together in another bowl.
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With the mixer on low, alternate adding the flour mixture (in 3 parts) and the cocoa mixture (in 2 parts) to the egg mixture.
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Beat until incorporated.
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13
In a small bowl, combine vinegar and baking soda and stir until baking soda dissolves; the mixture will fizz.
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Add to batter and stir until just combined.
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15
Fill each cupcake liner about 2/3 full with batter.
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Bake 20-25 minutes or until a toothpick inserted in the center comes out clean.
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Remove from oven, transfer to a wire rack, and let cool for 10 minutes.
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18
Remove cupcakes from pan, and let cool completely.
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19
To make the Buttercream: In a heavy bottomed saucepan, whisk the sugar and flour together.
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Add the milk and cream and cook over medium heat, whisking occasionally, until the mixture boils and has thickened, about 12 minutes.
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Transfer the mixture to the bowl of an electric mixer fitted with the paddle attachment.
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Beat on medium-high speed until cool, 5 minutes.
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Reduce the speed to low and add to the butter; beat until thoroughly incorporated.
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Increase speed to medium-high and beat until frosting is light and fluffy; 3 minutes.
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25
Add the vanilla and cinnamon and continue mixing until combined.
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26
If the frosting is too soft, transfer the bowl to the refrigerator to chill slightly, then beat again until it is the proper consistency.
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If the frosting is too firm, place the bowl over a pot of simmering water and beat with a wooden spoon until it is the proper consistency.
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28
Frost each cupcake with buttercream.
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29
Garnish with cinnamon imperials and white chocolate hearts if desired.