Preheat oven to 350F°. Prepare muffin pan with liners, set aside.
In a large bowl or stand mixer, cream butter and sugar. Add eggs, followed by vanilla. Mix well. Scrape sides of bowl occasionally. Add flour, baking powder and salt to your batter. It will thicken up rather quick. Slowly pour in milk, mix on low speed. Remember to scrape the sides of your bowl well and give it another quick mix.
Using a small cookie scoop for mini muffin cups or a large cookie scoop for regular and large muffin cups, fill your liners 2/3 of the way. If you fill completely you'll have some enormous cupcake tops. Cook mini cupcakes for 13 minutes and then begin checking every minute or so for doneness. Cook regular size cupcakes for 17 minutes and then begin checking. You want the edges to just begin to turn a golden color and a tooth pick to come out clean. You can also purchase a reusable metal cake checker. I find it to be one of those handy items to have if you do a lot of baking.
Cool for a few minutes before removing from your pan. Transfer to a wire rack to cool completely before frosting. Frosting possibilities are endless. I colored premade (yes I cheated here) frosting a light green for St. Patrick's Day, since it's right around the corner. You could also try this tasty double orange frosting.