To make Snickers chocolate cookies, mix together 1/2 cup plus 2 tablespoons of butter with 1/2 cup of brown sugar and 1/2 cup of granulated sugar until they form a light, fluffy mixture. Stir in 3/4 cup of peanut butter, 1 egg and 1 teaspoon of vanilla extract.
Sift together 1 1/4 cups of all-purpose flour, 1/2 cup of cocoa powder, 1 teaspoon of baking soda and 2 teaspoons of cornstarch. Combine the wet and dry ingredients, stirring until thoroughly incorporated.
Chop up 1/2 cup of mini Snickers bars, approximately 9 bars. Stir in the Snickers chunks with 1/3 cup of semisweet chocolate chunks, 1/3 cup of peanut butter chips and 1/3 cup of chopped caramel pieces, approximately 8 caramels. Allow the cookie dough to set in the refrigerator for a minimum of two hours, up to overnight.
To bake the cookies, preheat the oven to 350 degrees Fahrenheit. Line a baking sheet with parchment paper, and spoon the cookie dough onto it in balls of approximately 1 1/2 to 2 tablespoons. The cornstarch prevents the cookies from spreading much, so you can space the balls fairly close together.
Slightly flatten the dough balls, and then bake them for approximately eight minutes. The cookies are done when they firm up on the edges but the centers remain soft. Allow the cookies to cool slightly before serving.