Preheat the oven to 350° and line a regular sized muffin pan with 16 cupcake liners. Grab a large bowl, and use a hand or stand mixer to beat together butter, brown sugar and granulated sugar on high until mixed well.
Don’t mix any longer than 2 minutes. Next, add in eggs one at a time, beating after each egg. Put the mixer away, and fold in the vanilla extract. Be careful not to overmix.