Step 1

Preheat oven to 350°F. Line two dozen cupcake tins with paper liners.

Step 2

Whisk together margarita mix, tequila and Grand Marnier in a small bowl. Measure out 1¼ cups for the recipe; pour the rest on some ice and drink it while making the cupcakes.

Step 3

In a large bowl, use an electric mixer to combine the cake mix, egg whites, oil, lime zest and 1¼ cups of the margarita mix from step Blend on low for about 30 seconds and then increase speed to medium and blend for two additional minutes. Batter will be slightly lumpy.

Step 4

Spoon the batter into cupcake liners (about ¾½ full). Bake for 20 to 25 minutes, or until a toothpick inserted into the center comes out clean. Let the cupcakes cool for about 10 minutes in the pans, then remove them to a rack to cool completely.

Step 5

Place the butter in a large bowl and beat with electric mixer until the butter is fluffy. Add 5 cups of powdered sugar, lime juice, zest and salt. Mix until thick and creamy. Add more powdered sugar until the frosting is of a good spreading (or piping) consistency. Mix in a tiny amount of green food coloring or gel paste if you'd like the frosting to have a green tint. Ice the cupcakes in whatever manner you prefer... spreading or piping the frosting. Use small lime slices as garnish.