In a mixing bowl, beat together the butter and sugars until light and fluffy. Add the eggs and vanilla and beat an additional 2 minutes, until combined and creamy.
In a separate bowl, whisk together the flour, baking powder, baking soda and salt. Slowly add to the creamed mixture, stirring by hand just until combined.
By hand, stir in the candy bar pieces and the oats. (The dough is heavy and you may need to use your hands to quickly combine everything without over-stirring.)
Roll the dough into golf-ball sized balls and place at least an inch apart on baking sheets. Bake at 350 degrees for 11-13 minutes, until lightly golden brown. Cool for a minute on baking sheets before transferring to wire racks.
You can use whatever kind of candy bars you’d like in these cookies. I used 2 Milky Ways and 2 packages of Twix bars. Snickers or Reese’s peanut butter cups would definitely be great also! Use all of one kind or 4 different kinds – whatever sounds good to you!
This recipe makes about 3 dozen large cookies. You can half the recipe if you want, or just freeze the extra dough or cookies for another time!