Place the peppers, cut side down, on a grill tray and grill over/on a medium heat (approx. 200 °C, for approx. 10 mins. until the skin is charred and starts to bubble. Place the pepper in a bowl and cover with a damp cloth, leave to rest for approx. 10 mins. Carefully peel away the skin. Transfer the peppers and all the other ingredients up to and including the oil to a measuring cup, puree.
Sweet potato toast
Drizzle the sweet potatoes with oil, grill over/on a medium heat (approx. 200 °C for approx. 3 mins. on each side, season. Spread the muhammara on top and sprinkle with the mint and walnuts.