Chef Luptak includes kelp for a little seaside tang in this dish that will make you fall in love with tiny Brassica vegetables in a big way. If you can’t find kelp, use nori instead.
Per serving:
Preheat oven to 350 F (180 C). Line sheet pan with parchment paper.
Spread out mushrooms on prepared pan and roast for 30 minutes. Remove mushrooms from pan and set aside, leaving oven on. Place kelp on parchment paper-lined sheet pan and roast for 10 minutes.
In food processor, blend garlic and ginger with olive oil. Transfer to medium-sized pot and slowly caramelize over low heat, stirring frequently.
When kelp has finished roasting, transfer kelp and mushrooms to food processor and blend until minced.
Once ginger and garlic have caramelized, add kelp and mushroom mixture to pot. Add tamari, sesame oil, chilies, mirin, and vegetable stock, and cook for 10 minutes at a low simmer.
Check for seasoning, then cool and reserve. XO sauce will keep for 5 days in the fridge and also freezes well.
Preheat oven to 450 F (230 C). Line baking sheet with parchment paper.
Clean Brussels sprouts and cut in half. In large bowl, toss Brussels sprouts with olive oil, salt, and pepper. Transfer to prepared baking sheet and roast, cut side up, for 10 minutes.
Remove Brussels sprouts from oven and, while they’re still warm, toss with XO sauce. Garnish with shaved chestnuts, as well as thinly sliced radishes and microgreens, if desired. Serve immediately.