1. Preheat oven to 200°C (about 400°F) with the rack in the middle.
2. Mix softened butter, white miso paste, gochujang paste, garlic, chili flakes, vinegar, and honey thoroughly to create a thick marinade. Add a pinch of salt if desired.
3. Line a baking tray or roasting pan with aluminum foil. Pat chicken pieces dry, then place them skin-side down on the tray. Season with salt.
4. Rub half of the marinade onto the flesh side of each chicken piece. Flip chicken skin-side up, season again, and bake for 20 minutes.
5. Remove from oven, brush remaining marinade over the skin, and bake for an additional 15 to 20 minutes, or until the chicken reaches an internal temperature of at least 75°C (165°F) and the skin is golden brown.
6. If the chicken skin is browning too quickly, cover loosely with foil. For an extra crispy finish, switch the oven to the highest grill/broil setting for 2 to 3 minutes.
7. Transfer chicken to a serving platter. Mix pan juices with an additional tablespoon of gochujang and half a teaspoon of honey to make a spicy-sweet gravy. Pour this sauce over the chicken and squeeze fresh lemon juice on top. Serve with extra lemon wedges.