Preheat your oven to 200°C. Chop the potatoes into 2cm wide wedges (no need to peel). Pop the wedges on a large baking tray. Drizzle with oil, then season with salt and pepper. Toss to coat, then spread out in a single layer and roast on the top shelf of your oven until golden, 25-30 mins. Turn halfway through cooking. TIP: Use two baking trays if necessary, you want the potatoes nicely spread out.

Halve, peel and thinly slice the onion. Trim the root from the baby gem lettuce, reserve 2-3 whole leaves per person then halve lengthways, then thinly slice widthways. Heat a drizzle of oil in a large frying pan on medium-high heat. Once hot, add the onion and fry until golden and soft, 6-8 mins, stirring occasionally. While the onion fries, thinly slice the mushrooms, peel and grate the garlic (or use a garlic press). Halve the tomatoes and finely chop the parsley (stalks and all). Grate the cheese.

Once the onion has cooked, transfer to a bowl and pop your pan back on medium-high heat. Add another drizzle of oil and pop in the mushrooms. Season with salt and pepper and fry until golden brown, 6-8 mins. Don't stir too often to give them a chance to brown. TIP: Cook the mushrooms in batches if necessary - you want them to fry, not stew. If cooking in batches, you may need to add more oil.

Meanwhile, pop the tomatoes, parsley, sliced baby gem, olive oil (see ingredients for amount) and half the red wine vinegar into a bowl. Season with salt, pepper and a pinch of sugar (if you have any). Mix together and set aside. Halve the burger buns.

Once the mushrooms are nicely browned (increase the heat if there's still some liquid in the pan and allow it to evaporate), add the garlic and cooked onion to the pan. Stir together and cook for 1 min. Add the remaining vinegar and allow it to evaporate, 1 min, then add the BBQ sauce and stir together so everything is well mixed. Remove from the heat. Taste and add salt and pepper if needed. Pop the burger bun bases onto a baking tray and sprinkle the bottom buns with cheese.

Once your potatoes are ready, move the tray to the bottom shelf of your oven. Add the burger bun tops to the tray to warm through. Heat the grill to high. Pop the cheese-topped burger bun bases under the grill and cook until the cheese is bubbly, melted and golden, 2-3 mins. Remove from the grill, place 2-3 baby gem leaves onto the cheese, and divide the mushroom mixture between them, pop the bun lids on top. Serve the mushroom buns with the wedges and the tomato salad alongside. Enjoy!