01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
03 - In a large bowl, beat butter and sugar together until light and fluffy, about 2–3 minutes.
04 - Add eggs one at a time, beating well after each. Mix in vanilla and peppermint extracts.
05 - In a small bowl, whisk together milk and sour cream.
06 - Add dry ingredients to the butter mixture in three additions, alternating with the milk mixture, beginning and ending with dry ingredients. Mix until just combined.
07 - Add a few drops of green food coloring and gently fold until evenly tinted.
08 - Divide batter evenly among cupcake liners, filling about 2/3 full each.
09 - Bake for 16–18 minutes, or until a toothpick inserted in the center comes out clean. Cool in pan for 5 minutes, then transfer to a wire rack to cool completely.
10 - Beat butter until smooth and creamy. Gradually add powdered sugar, beating until incorporated.
11 - Mix in milk, peppermint and vanilla extracts, salt, and a few drops of green food coloring. Beat until fluffy and smooth.
12 - Pipe or spread frosting onto cooled cupcakes. Garnish with sprinkles, cherries, and mini straws if desired.