Preheat oven to 180C. Grease or line 2 x 12 cup muffin pans with paper cups.
Beat butter and sugar until well combined.
Add all remaining ingredients, and mix on low until combined. Increase speed to high and mix for 3 minutes. Stir through choc chips.
Fill muffin cups 3/4 full, and bake for 20-25 minutes, until cake springs back when pressed lightly. Allow to cool completely before icing.
Prepare Queen Buttercream Icing as per packet instructions. Add 1/4 teaspoon green colour gel and mix until combined. Pipe onto cupcakes using a star tip and finish with extra choc chips (optional).