Scoop out your desired flavor of ice cream (I like this brand for storebought) using a large ice cream scoop, so that you are forming a solid sphere that's about 1 serving size. (allysonkramer.com)
Using a large ice cream scoop, fill the muffin cups with the batter. (crumbtopbaking.com)
I use a cookie scooper for the mini muffins and a larger ice cream scoop for the regular muffins. (strawberriesforsupper.com)