Preheat the oven to 350°F. Line a cupcake pan with cupcake liners.

In a large mixing bowl, combine the sugar, vegetable oil, egg, egg yolk, vanilla extract, and mint extract. Beat on medium speed until well incorporated, about 2 minutes.

Mix in the sour cream and beat until well combined.

In a separate bowl, combine the dry ingredients. Alternate adding half the dry ingredients and half the liquid ingredients at a time, mixing just until incorporated. Add the green food coloring and mix until combined.

Using a large cookie scoop, divide the batter evenly, filling each liner 2/3 full. Bake for 14-16 minutes. Test for doneness with a toothpick.

Cool completely before frosting.

Cut the butter into pieces. Using the paddle attachment, whip the butter for 5-7 minutes until very fluffy.

Add the vanilla malt powder and 2 cups of powdered sugar, vanilla extract, and heavy cream. Beat until well combined and fluffy.

Add the remaining powdered sugar, Baileys, and a pinch of salt. Whip for 2-3 minutes until smooth.

Frost the cooled cupcakes.