Cream butter, sugar, eggs, and vanilla. Stir in melted chocolate. Stir in flour until fully incorporated. Add in the Hershey's syrup, heath bar bits (*reserve ¼ cup heath bits) and pecans until combined.
Pour batter into prepared dish and set aside. Finely chop reserved heath bar bits and sprinkle on top of batter. Bake at 350’ for 30 minutes.