First, prepare marinade by mixing all ingredients together in bowl until well combined. Check seasoning; add more aji rocoto paste or salt, if desired.
Coat poussin (or chicken thighs, if using) thoroughly in half of marinade. Allow to marinate at least 6 hours or overnight in fridge.
Preheat oven to 400°F and line roasting tray with foil.
Remove excess marinade from poussin and reserve for basting during cooking. Place pieces on roasting tray, skin side up, and coat liberally with Maldon sea salt flakes. Place in oven and cook 20 minutes, basting poussin every 5 minutes with reserved marinade. Check doneness of poussin by piercing knife in thickest part of thigh. (The juices should run golden and clear. If you have a meat thermometer, the internal temperature should be between 167°F and 176°F.)
When ready, place poussin in broiler 5 minutes to crisp up skin. Remove tray from broiler and let meat rest 2 – 3 minutes.
Meanwhile, quickly bring remaining half of marinade to boil with sugar. Add coconut cream and heat through, mixing well. Remove from heat.
Plate poussin, drizzle piri-piri and coconut cream sauce over each, finish with scattering of cilantro, and serve with lemon wedges.