Preheat oven to 350°F. Line cookie sheets with parchment paper or spray lightly with cooking spray.

In a large mixing bowl, whisk together the sugar cookie mix, all-purpose flour, and cornstarch until combined.

Add the melted butter and eggs to the dry ingredients. Use an electric mixer on high speed with a paddle attachment to mix until a soft dough forms.

Fold in the chopped Heath bar bits (or your preferred chocolate and toffee candy).

Using a 1 1/2 Tablespoon cookie scoop, form cookie dough balls and place them evenly across the prepared cookie sheets, leaving about an inch of space between each one.

Bake in the preheated oven for 10-12 minutes or until the edges are golden brown.

Allow the cookies to cool on the baking sheet for 5-10 minutes, then transfer to a cooling rack or serve warm.