Mix all the marinade ingredients together in a large bowl.
Peel the butternut and sweet potatoes, then slice in pieces no bigger than ½-¾cm/¼-½in thick.
Dice the remaining vegetables to the same size.
Submerge all the vegetables in the marinade for 2 hours.
Take the vegetables out of the marinade and remove any excess liquid.
Place the griddle pan or frying pan on the hob and drizzle with a little olive oil, ensure the pan is hot.
Place the vegetables in the pan and grill for 2-3 minutes.