I add the crumbs from 3-6 graham crackers into the peanut butter mixture, and I use vanilla Almond Bark instead of the white chips

What I did was I let the final icing layer set at room temp for several hours prior to putting it in the fridge. I let it set overnight and then when I took it out I let it get to room temp (approx 1 hour) then cut with a paring knife.