Preheat the oven to 200˚C/gas mark 6.
Place the tomatoes on a baking sheet. Sprinkle over 1 teaspoon each of salt and pepper, the allspice, balsamic vinegar, brown sugar and oil and roast for 1 hour. Remove from the oven and set aside to cool before pressing through a sieve. Season and chill until needed – the ketchup will keep for two days.
Slice the potatoes into thick wedges and place in a roasting tin. Whisk together the Dijon mustard, oil, cider vinegar, rosemary, 1 teaspoon salt and some freshly ground black pepper. Pour the mixture over the wedges and toss to coat thoroughly. Roast for 1 hour, shaking the tin occasionally so the wedges don’t stick. Season again when they are removed from oven.
For the mushroom burger stuffing, heat the oil and vegan butter/margarine in a medium-sized, non-stick, heavy-based frying pan and add the onion Season and sauté gently until it begins to soften. Remove the stalks from the portobello mushrooms, finely chop and add to the pan. Sweat the onion and mushroom stalks for a minute or two before adding the garlic and thyme. Season generously and cook for a few more minutes.
Add the breadcrumbs to the pan along with the vegan butter/margarine and red wine vinegar. Let the breadcrumbs fry for a few minutes until golden before finally adding the toasted pine nuts and freshly chopped parsley.
Lightly grease a baking tray. Rub the mushrooms with oil and season the outsides with salt and pepper. Divide the breadcrumb mixture between them and pack it in tightly using the back of a spoon or your fingers. Place on the baking tray and bake in the oven with the wedges for the last 30 minutes of their cooking time.
Spread a little ketchup in each roll and serve the burgers in them with a
handful of rocket leaves and the potato wedges on the side.