Step 1: Prep the Oven and Tin
Set a rack in the center of your oven and preheat to 350°F. Line a 12-cup muffin tin with paper liners—this keeps your St. Patrick’s Day Cupcakes from sticking and adds a cute touch.

Step 2: Mix the Dry Ingredients
In a medium bowl, whisk the flour, baking powder, baking soda, and salt until blended—no clumps allowed. This dry mix is the foundation for that fluffy texture.

Step 3: Cream the Wet Base
In a large bowl, use your handheld mixer on medium-high to beat the granulated sugar and butter until light and fluffy—3 to 4 minutes. Add the egg whites and vanilla, beating for 2 minutes until smooth. Mix in the sour cream until just combined—it’s the secret to moist St. Patrick’s Day Cupcakes.

Step 4: Combine and Fill
Add half the dry ingredients to the wet, beating on low until just mixed. Pour in the milk and beat again, then add the remaining dry mix—stop when it’s just combined to keep it tender. Fill the liners three-quarters full with batter—use a scoop for evenness.

Step 5: Bake and Cool
Bake for 19 to 22 minutes, until slightly golden and a tester comes out clean. Remove from the tin and cool completely on a rack—patience here makes frosting a breeze.

Step 6: Whip the Frosting
In a large bowl, beat the butter on medium-high until fluffy. Add confectioners’ sugar, then the cream, vanilla, and salt—beat until smooth and creamy. Scoop 1 cup into a piping bag with a star tip. Add green food coloring to the rest, stirring until you hit that shamrock shade, then transfer to a bag with a large round tip.

Step 7: Decorate with Flair
Pipe green frosting onto each cupcake in a swirl. Stand a 3-inch rainbow candy piece upright in the center. Pipe white frosting clouds at each end with the star tip, then sprinkle with gold—your St. Patrick’s Day Cupcakes are now leprechaun-ready.