Preheat oven to 350 degrees.
Beat sugar and butter together in a bowl until light and creamy. ~8 minutes.
Add egg and vanilla, and continue beating until well incorporated.
Mix together flour, cocoa, and baking soda and add to the mixture, continuing to beat,
Add melted chocolate and mix further.
Add chopped SNICKERS® and stir just enough to incorporate without smashing the pieces.
Let dough chill in the refrigerator for 15 minutes.
Scoop out ~2 tablespoon cookie dough and roll it into a ball, then place on parchment lined baking sheet, leaving room for the cookies to flatten and expand.
Bake 10-12 minutes.
Remove from oven and let cool.