Margarita cupcakes - cyndy's easy recipe for beginners

Ingredients

• 9 ounces liquid Margarita mix
• 3 ounces tequila
• ¾ ounce Grand Marnier
• 1 box white cake mix
• 3 large egg whites
• 2 Tbs vegetable oil
• 1 Tbs. lime zest
• 2 sticks unsalted butter, at room temperature
• 5 to 6 cups powdered sugar
• 2 Tbs. fresh lime juice
• 1/8 tsp. salt
• 1 tsp. grated lime zest
• green food coloring, if desired
• small lime slices for garnish, if desired
• 1/2 jigger of Grand Marnier