Individually wrap the sweet potatoes and garlic in foil.
Gas/electric grill: Grill the garlic and sweet potatoes on the warming rack over a medium heat for approx. 50 mins. Mix the prawns with the oil and thyme, cook on the grill for approx. 2 mins. on each side. Place the chorizo on top of the prawns, heat through for approx. 30 secs. Push the cloves of garlic into a bowl, crush with a fork, stir in the sour single cream, season. Cut open the potatoes, top with the sauce, serve with the prawns and chorizo.