Put the poussin in a large non-metallic bowl and add the olive oil, cumin, garlic powder and paprika. Massage the marinade into the poussin, cover and leave in the fridge to marinate for at least 2 hours, but preferably overnight.
Heat a large frying pan over a medium–low heat. Lay the poussin in the pan, skin-side up and cook for 5 minutes, or until browned. Turn the poussin over, place a heavy weight on the top and leave to cook for 30–45 minutes, or until crispy and cooked through. Remove from the pan, cover and allow to rest.
Meanwhile, heat a griddle pan or a grill and brush the corn on the cob with oil. Grill, turning frequently, until chargrilled on all sides.
Cut the kernels off the cob and mix with the remaining salsa ingredients in a small bowl. Season with salt and pepper.
To make the buttermilk hot sauce, mix together the chipotle purée, vinegar and sugar. Add the buttermilk, mayonnaise and a squeeze of lime juice and stir well until combined.
To serve, cut the poussin in half, scatter over the salsa and serve with the buttermilk hot sauce on the side.