Bake the sweet potatoes in aluminium foil on the grill until they are tender, about 40 minutes with the BBQ lid closed. Once cooked, cut the potatoes lengthwise and grill them on the cut side for a while to get beautiful grill marks.
Clean the celery and finely slice the stalks, total 250 g. Cut the apricots into thin slices.
Bring the water to a boil and cook the diced sweet potato in a closed pot for 6 minutes until tender. Dissolve the sugar in the cooking water and add the pieces of celery and apricot.
Add the grated ginger, vinegar, mustard seeds, curry and salt. Stir the mixture and simmer until it thickens.
Serve the BBQ-roasted sweet potatoes with a dollop of crème fraiche (omit for a vegan option) and chutney.