Ignite the charcoal in the Big Green Egg and leave the lid open for 14-15 minutes. Meanwhile, wash the sweet potatoes.Place the convEGGtor and the grid in the EGG and close the lid. Heat to 190°C.Place the sweet potatoes on the grid, close the lid of the EGG and leave to roast for approximately 60 minutes. The potatoes are cooked when they feel soft. Meanwhile, pull the leaves off the lemon thyme and chop finely.Remove the sweet potatoes from the EGG and make an incision in the top. Spoon the flesh out of the skins and mash finely using a fork. Mix with the lemon thyme and honey and add coarse sea salt and black pepper to taste. Return the mashed potatoes to the skins and top each with a tablespoon of crème fraîche.