Heat oven to 425°F and line a baking sheet with foil
In a large bowl, whisk miso, maple syrup, olive oil, and cumin until smooth, reserving about 3 Tbsp of the marinade
Add Brussels sprouts and chicken and toss to coat
Spread everything in a single layer on the baking sheet, scraping any extra marinade on top
Bake for 8 minutes
Remove and spoon the reserved marinade over the chicken and sprouts
Return to the oven for 4 more minutes
Switch to broil and cook 1–2 minutes until the chicken is cooked through and lightly charred
Serve warm
