Line 2 baking sheets with parchment. Spread the peanuts on one sheet and warm in a 300°F (150°C) oven for 5 minutes to take off the chill—this helps the coating cling.
Set a heatproof bowl over a saucepan with 1 inch of barely simmering water (do not let the bowl touch the water). Add the chocolate and butterscotch chips and stir gently until about 75% melted, 3 to 4 minutes. Remove the bowl from the pan and continue stirring until smooth. Tip: Wipe the bottom of the bowl so no water drips into the chocolate.
Off the heat, stir in the crunchy peanut butter and vanilla until the mixture is glossy and fully combined, 30 to 60 seconds.
Fold the warmed peanuts into the chocolate mixture until every peanut is well coated.
Using a 1-tablespoon cookie scoop or two small spoons, portion mounds onto the clean lined baking sheet, leaving a little space between each. Lightly tap the pan on the counter to settle the clusters, then sprinkle with a few flakes of sea salt.
Refrigerate the tray for 10 to 12 minutes to set, then bring the clusters back to room temperature for 5 to 10 minutes before serving for the best snap and flavor.