Preheat your oven to 200ºC/Gas 6. Place a roasting tray in the top shelf to heat up.
Cut your peppers into 3cm-thick slices, discarding seeds, stem and white membranes. Quarter your onions and strip off the skins.
Tumble this veg into your warmed roasting tray, with the tomatoes and garlic cloves (left whole and in their skins). Gloss with oil. Season well. Roast 25 mins or till tender and charred around the edges.
Strip the roasted garlic cloves from their papery skins. Transfer all the veg into a blender or food processor with the water or stock. Add the ras el hanout and a small handful of your mint. Blend till smooth. Taste. Adjust seasoning and spicing to your liking.
Garnish with a few mint leaves.