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1
Preheat the oven to 350F (180C).
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2
Line 12 standard muffin tins with cupcake liners or sprayed with cooking spray.
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3
Add the butter, root beer, and cocoa in a microwave-safe bowl, cover with plastic wrap, and microwave on HIGH until the butter melts, about 2 minutes.
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4
Stir to combine.
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5
Meanwhile, mix together the flour, sugar, baking powder, baking soda, and salt in a large bowl.
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6
Combine the sour cream, eggs, and vanilla together in a small bowl.
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7
Stir in the hot cocoa mixture into the dry ingredients.
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8
Stir in the sour cream mixture just to combine, do not to overmix.
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9
Divide the batter evenly between the prepared muffin cups, filling each one about 3/4 of the way full, about 1/4 cup per cupcake.
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10
Bake cupcakes until a wooden stick or toothpick inserted in the center of the cake comes out clean, 24 to 26 minutes.
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11
Cool the cupcakes completely in the tin on a rack.
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12
Remove from liners and transfer cupcakes onto a wire rack.
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13
Frosting:
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14
Bring a few inches of water to a boil in a saucepan that can hold a mixer's bowl above the water.
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15
Mix the egg whites, sugar, cream of tartar, and salt in the bowl by hand, whisk until well combined.
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16
Set the bowl above the boiling water and continue whisking until the mixture is hot to the touch and the sugar dissolves, about 1 to 2 minutes.
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17
Transfer the mixture to a standing mixer fitted with the whisk attachment and beat at medium-high speed until eggs beat up into a cool stiff meringue, about 5 minutes.
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18
Add a few drops of desired extract and/or food coloring and lightly beat into the meringue.
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19
Decorate:
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20
Using a spoon, offset spatula or piping bag, dollop, spread or pipe about 1/2 cup meringue on top of each cupcake to make a ghost or monster of your choice.
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21
Decorate with candied eyeballs or other candies.
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22
These cupcakes can be finished 2 to 3 hours in advance and held at room temperature.
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23
Make 12 cupcakes.
