Transfer the mixture to a parchment lined 8" x 8" baking pan. Press the mixture firmly into the bottom of the pan, making sure to get it into the corners.
Pour the melted chocolate on top and garnish with desired toppings.
Place the pan in the freezer and freeze for at least 2 hours. When ready to serve, remove the bars from the pan and cut into squares. Store in the freezer for best texture.