Seed and roughly chop bell pepper, Serrano chilies, and jalapeño chilies. 

Add bell pepper, chilies, garlic, blackening seasoning, cilantro, basil, oil, and lemon juice to a food processor or blender. Whirl until marinade is fairly smooth but still has some small chunks. Taste marinade; if the blackening seasoning you used was unsalted, you may want to add salt. Set aside ¼ cup marinade in the refrigerator for basting later.

Put chicken in a large zip-top bag. Add remaining peri peri marinade. Squeeze out air from bag, seal bag, and gently toss chicken to be sure it’s evenly coated all over.

Refrigerate chicken in marinade at least 30 minutes and up to 24 hours. The longer it marinates, the more flavorful it will be.

Set out chicken at room temperature. Set up a grill for direct heat cooking over medium heat (350°-400°F), preferably using lump charcoal. Remove chicken from marinade and discard marinade.

Using grill tongs and a wad of oiled paper towels, lightly oil cooking grate to prevent sticking. Cook chicken over hot coals, turning every 5-6 minutes to prevent it from burning, until chicken reaches about 10°F below your final temperature (cook to 150°F in the thickest part of the breast or 155°F in the thickest part of the thigh not touching bone), 40-50 minutes.

Baste chicken with half of reserved peri peri marinade and cook 5 minutes. Turn chicken over, baste with remaining marinade, and cook until chicken reaches 160°F in the thickest part of the breast and at least 165°F in the legs and thighs, about 5 minutes more.

If you like, cut chicken into smaller pieces and season with more salt, then serve.