For Cupcakes

• Preheat oven to 350 degrees F. Line 24 cupcake cups with liners.
• Bring the Guinness and butter to a simmer in a saucepan over medium heat.
• Add the cocoa powder and whisk until smooth. Remove from heat and allow to cool slightly.
• Whisk flour, sugar, baking soda and salt in a large bowl.
• Using an electric mixer, beat the eggs and sour cream on medium speed until combined.
• Add the Guinness mixture to the egg mixture and beat just to combine.
• Reduce the speed to low, add the flour mixture and beat briefly.
• Using a rubber spatula, fold the batter until completely combined.
• Divide the batter among the cupcake liners.
• Bake until a toothpick inserted into the center comes out clean, 15-18 minutes. Cool completely.

For Whiskey Ganache Filling

• Place 1 oz pieces of chocolate in a heatproof bowl.
• Heat the cream slowly until simmering and pour it over the chocolate. Let it sit for one minute and then, using a rubber spatula, stir it until smooth.
• Add the butter and whiskey; stir until combined.
• Let the ganache cool until thick but still soft enough to be piped. (Refrigerate if necessary)

Fill the Cupcakes

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• Using a 1-inch round cookie cutter (or a small paring knife), cut the centers out of the cooled cupcakes, going about two-thirds of the way down.
• Transfer the ganache to a piping bag with a wide tip and fill the holes in each cupcake over the top. creating a soft peak.
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For Irish Cream Frosting

• With hand mixer, whip the butter on medium-high speed for 5 minutes, scraping the sides of the bowl occasionally.
• Reduce the speed to medium-low and gradually add the powdered sugar- a few tablespoons at a time- until all of it is incorporated.
• Add the Irish Cream, increase the speed to medium-high and whip for another 2 to 3 minutes, until it is light and fluffy.
• Frost the cupcakes; add chocolate shavings or sprinkles if desired.
• Store the cupcakes in an airtight container, refrigerated, for up to 3 days.
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