Twix Cookies

2 cups flour
1/2 tsp baking soda
1/2 tsp salt
3/4  cup melted (and then cooled) butter
1 cup packed brown sugar
1/2 cup sugar
1 egg, plus 1 egg yolk
2 tsp vanilla
2 cups chopped Twix bars

1. Preheat oven to 325F. Coarsely chop Twix bars in 1/4 inch chunks.
2. Whisk together the flour, baking soda and salt in a medium bowl. Set aside.
3. In a large bowl, beat together butter, sugar and brown sugar. Beat in the egg, egg yolk and vanilla. Fold in flour, then fold in the chopped Twix bars.
4. These cookies look best if you use this method from Sprinkled With Flour: Grab a scant 1/2 cup of dough and roll it into a ball. Then, using your fingertips, pull apart the dough into two equal halves. Place on cookie sheets with the jagged edges facing up.
5. Bake for 15-18 minutes, or until the cookies are lightly browned.