When the potatoes are almost tender, heat the remaining tablespoon of oil in a large frying pan over a medium high heat. Add the courgette, squash, mushrooms, onions & salt and pepper and cook, stirring occasionally, until just tender and golden brown, around 6 minutes

Preheat the grill / broiler. Halve the potatoes, transfer to a baking dish cut side up and top with the vegetable mixture. Pour some warmed marinara sauce over the potatoes then top with as much cheese as you like. Grill until the cheese is melted and bubbly, 2 or 3 minutes, then transfer to plates and serve

For the marinara, place the tomatoes, tomato paste, minced garlic, oregano, salt, and pepper in a blender and blitz until smooth. Saute the finely chopped onion in olive oil for 2 minutes in a large frying pan. Add the blended tomato sauce, basil and white wine. Simmer for 30 minutes, stirring occasionally. This makes twice as much as needed in this recipe but you can freeze the half you don't need for another time