Line an 8 or 9-inch square pan with wax or parchment paper, leaving an overhang on the long sides.
Microwave chocolate in a large bowl, in 30-second increments at 50% power, stirring in between, until smooth. Fold in 2 cups of the toppings. Transfer mixture to the pan, pressing lightly until even.
Scatter over remaining toppings and refrigerate until set, about 30 minutes. Let sit at room temperature for 10 minutes then slice into 16 2-inch squares. Store in the refrigerator. Store in the refrigerator for up to 2 weeks.