Add ingredients for chicken marinade to a blender and blitz until smooth.
Add chicken to a zippered bag or food storage container and pour marinade over top. Let marinade in the refrigerator for at least 30 minutes (up to overnight).
Add ingredients for the peanut sauce to a blender and blitz until smooth. Transfer the sauce to an airtight container (like a mason jar) and store in refrigerator for up to two weeks.
Preheat grill to high heat (400degF).
Remove chicken from marinade and place on hot grill. Cook for 7-8 minutes on each side or until temperature probe reads at least 165degF in center of thickest piece.
Remove from grill and serve with drizzle of peanut sauce and cilantro leaves.