Ingredients:

CUPCAKES - MAKES 10-12 CUPCAKES
6 tbsp butter, softened
2/3 cup sugar
3 egg whites
1/2 cup sour cream
1 tsp vanilla extract
1 cup + 2 tbsp all purpose flour
1 & 1/2 tsp baking powder
1/4 tsp salt
leaf green food coloring by wilton (or similar light green food coloring)
BUTTERCREAM
2 sticks of butter, unsalted at room temperature
1/2 cup vegetable shortening (can substitute butter)
3-4 cups powdered sugar
1/2 tsp of powdered watermelon koolaid mix
small about of red food coloring, to give the buttercream a pinkish color
mini chocolate chips
Directions:

CUPCAKES
Preheat the oven to 375º F. Place cupcakes liners to muffin pan.
In a mixing bowl, combine the butter and sugar, beat using an electric mixer until fluffy. Add in the egg whites, beat again.
Add in the sour cream and vanilla extract, mix by hand with spatula.
In a smaller bowl, combine the flour, baking powder and salt, gently mix with a spoon.
Gradually add half of the flour mixture to the wet ingredients, do not dump it in, rather take spoonfuls of the flour mixture and gently shake it over the wet ingredients, as if you were sifting in the flour. Fold in the mixture until no flour remains. Repeat with the other half of the flour, folding it in and scraping the sides and bottom of the bowl to incorporate everything.
Add in the green food coloring, mix to incorporate.
Divide the batter among the cupcake liners, filling each 1/2 full.
Bake at 375º F for 5 minutes, then reduce heat to 350º will keeping the cupcakes in the oven and bake for 8-10 minutes or until a toothpick comes out clean when inserted into the center of a cupcake.
Allow the cupcakes to cool before adding the buttercream.
BUTTERCREAM
In a mixing bowl beat the butter and vegetable shortening with an electric mixer until smooth, about 2 minutes.
Add in 2 cups of powdered sugar, mix by hand with a spatula.
Add in more powdered sugar as you see fit, up to 2 more cups, mixing first by hand then with an electric mixer.
Add in the watermelon kool aid powder and a small amount of red food coloring (to give the frosting a pinkish color), mixing one last time with an electric mixer.

HOW TO ASSEMBLE
Place the buttercream in a large piping bag fit with a 1m wilton piping tip. Push the buttercream down into the bag. Pipe the buttercream onto the cupcakes, starting in the center of the cupcake, swirling out, and then swirling back into the center, progressively stacking the frosting as you get to the center.
Add mini chocolate chips on top of the buttercream.
If the temperature is going to be really hot when serving these, it is best to add vegetable shortening to the buttercream because it will give the buttercream stability. An all butter buttercream can become "melty" or "floppy" in high heat.