Preheat the oven to 425 F. Place the Brussels sprouts on a rimmed baking sheet and drizzle with 2 tablespoons oil, toss, then spread out on the baking sheet. Season with salt and pepper and roast for 20 to 25 minutes until tender and the edges are browned.
Meanwhile, heat the remaining tablespoon of oil in a small saucepan or skillet over medium heat and add the garlic, scallions, and ginger. Stir for 60 seconds until you can smell the garlic and ginger, then add the hot sauce, soy sauce, honey, and vinegar and bring to a simmer.
When the Brussels sprouts are cooked, pour the sauce over and stir to coat them. Transfer to a bowl and top with the crushed peanuts.
Notes
I didn’t have the traditional chili peppers or Sichuan peppercorns (which I find a bit overpowering), so I reached for my trusty bottle of Gochujang sauce (a Korean hot sauce; it is also commonly available as a paste). Any hot sauce will do; Sriracha is great, and red pepper flakes will also work just fine.