In a medium-sized bowl mix the flour, baking powder, baking soda, salt and set it aside.
Cream butter and sugar with your electric/stand mixer until fluffy.
Add the eggs and egg whites one at a time and mix on slow speed.
Add vanilla and mint extracts and vegetable oil and mix until blended.
On slow speed add the contents of the medium-sized bowl, don't over mix.
Add milk and mix for about 30 seconds on slow, then scrap the bowl (including the bottom) and mix again for another 30 seconds. The batter should be smooth.
Scoop about 1/4 cup of batter into your cupcake liners.
Bake 20-22 minutes at 325 degrees.
Allow to cool before frosting.
Frosting
Beat the butter for a few minutes using your mixer on medium speed.
Add 3 cups of powdered sugar and mix on low speed until blended.
Add the mint extract, salt, and 2 tablespoons of milk. Mix on medium speed for 3 minutes.
If you need stiffer frosting, add the remaining sugar.
If you need a thinner frosting, add the remaining milk.
Add your food coloring gel until you get the color desired. (optional)