Vanilla ice cream and hot chocolate sauce, for serving
Preheat the oven to 350°. Generously oil a rimmed baking sheet. In a bowl, toss the crisped rice and peanuts with the corn syrup until evenly coated; add a pinch of salt. Spread the mixture as thinly as possible on the baking sheet and bake for 10 minutes, until crisp. While still warm, transfer the crunch to a plate; let cool. Break the crunch into large pieces.
Scoop vanilla ice cream into sundae glasses and pour hot chocolate sauce on top. Top with the crunch and serve.
The crunch can be stored overnight in an airtight container.