In a large bowl, combine flour, baking powder, and salt, whisk, and set aside.
In another bowl, cream together butter and sugar until fluffy
Add vanilla and eggs, mix until combined.
Add in dry ingredients and milk, alternating and mixing in between each addition.
Fill cupcake liners 2/3 full.
Bake 18-20 minutes. Allow cupcakes to cool.
Add milk slowly until frosting is the perfect consistency.
Once cupcakes are cooled, cut a small piece out of the top.
Fill with M&Ms, and trim the fluffy end of the piece you removed and just place the top of the cupcake back.
Top the cupcakes with frosting and add sprinkles if desired. Enjoy!