Step 1: Prepare the Oven and Cupcake Pan

Preheat your oven to 350°F (175°C). This temperature ensures that the cupcakes bake evenly and rise properly. Line a 12-cupcake pan with cupcake liners. Using liners makes it easier to remove the cupcakes and prevents them from sticking to the pan. If you don't have cupcake liners, you can grease the pan thoroughly with butter or cooking spray.

Step 2: Whisk the Dry Ingredients

In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. This step helps to evenly distribute the baking powder and salt throughout the flour, ensuring a consistent texture and rise. Whisking also aerates the flour, making it lighter.

Step 3: Cream Butter and Sugar

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. This is a crucial step for creating a tender and moist cupcake. Using softened butter is essential for achieving the right consistency. Creaming incorporates air into the mixture, which helps the cupcakes rise and creates a light, airy texture. An electric mixer (handheld or stand mixer) is recommended for this step, but you can also do it by hand if you don't have a mixer.

Step 4: Add Eggs and Vanilla

Add the eggs to the creamed butter and sugar mixture, one at a time, mixing well after each addition. This ensures that the eggs are fully incorporated and that the mixture remains smooth. Stir in the vanilla extract, which enhances the flavor of the cupcakes.

Step 5: Alternate Adding Dry and Wet Ingredients

Gradually add the flour mixture to the wet ingredients, alternating with the milk, starting and ending with the flour. This technique prevents the batter from becoming overmixed, which can result in tough cupcakes. Mix until just combined – be careful not to overmix.

Step 6: Fill Cupcake Liners

Divide the batter evenly among the cupcake liners, filling each about ⅔ full. This allows the cupcakes to rise properly without overflowing. You can use an ice cream scoop or a measuring cup to ensure even filling.

Step 7: Bake the Cupcakes

Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. This is the best way to check if the cupcakes are done. If the toothpick comes out with wet batter, continue baking for a few more minutes.

Step 8: Cool the Cupcakes

Let the cupcakes cool completely on a wire rack before decorating. This prevents the frosting from melting and makes the cupcakes easier to handle. Allow them to cool in the pan for a few minutes before transferring them to the wire rack.

Step 9: Prepare the Green Buttercream Frosting

In a large bowl, beat the softened butter until smooth and creamy. Gradually add the powdered sugar, one cup at a time, and beat until fully incorporated. This creates a smooth and stable frosting. Add the vanilla extract and 3 tablespoons of milk. Add more milk, one tablespoon at a time, until you reach a spreadable consistency. Be careful not to add too much milk, as this can make the frosting too runny. Add green food coloring, a few drops at a time, until you achieve the desired shade of green. Gel food coloring is recommended, as it provides a more vibrant color without adding excess liquid.

Step 10: Frost the Cupcakes

Once the cupcakes are completely cooled, frost them generously with the green buttercream frosting. You can use a spatula, a butter knife, or a piping bag to apply the frosting. For a more professional look, use a piping bag fitted with a decorative tip.

Step 11: Add the Rainbow Decoration

Take rainbow candy strips (such as Airheads Xtremes) and cut them into pieces long enough to form a small arch on top of each cupcake. Gently press both ends of the rainbow strip into the icing to create a rainbow arch.

Step 12: Add Gold Sprinkles (Optional)

Sprinkle edible gold flakes, dazzle dust, or gold sprinkles at the ends of the rainbow arch. This adds a touch of sparkle and completes the St. Patrick's Day theme. You can also use liquorice candy to resemble a vessel/pot of gold and add sprinkles and/or gold flakes on top.