Rinse the grapes and pat every side thoroughly with paper towels. The skins should look matte and feel dry rather than slick.

Heat the caramels with the cream in a small pot over medium heat, stirring frequently for about 5 minutes. The mixture is ready when it looks smooth and glossy.

Spread the peanuts on a plate, secure a grape on a toothpick, and lower it into the caramel until the coating reaches at least halfway up its sides; let excess caramel drip back into the pot, then dip the bottom in peanuts and place it on a parchment-lined baking sheet. A thin, even coating should stay on the grape without pooling heavily underneath.

Warm the caramel over low heat if it thickens as you work, and refrigerate the finished grapes if you are not serving them right away; for making them 1 day ahead, transfer them to an airtight container and keep refrigerated. The coating should hold its shape and the grapes should remain crisp.