Preheat the oven to 220°C (200°C fan-forced). Heat 2 tbsp olive oil in a medium frypan over medium-high heat. Add the mushrooms and half the onions and fry for 4-5 mins. Add 1 cup passata and simmer for 2-3 mins to heat through. Season well with salt and pepper.
Lightly brush a 20 cm springform cake pan with olive oil. Carefully lay the first tortilla on the bottom of the pan, allowing it to come up the sides. Layer 1 cup of cheese with half of the sliced chicken. Finish with the ham, salami and passata mixture. Scatter with another ½ cup of cheese and drizzle with 1 tbsp barbecue sauce.
Trim the other jumbo tortilla to fit the cake pan. Top the pizzarito with the tortilla, then spread ¼ cup passata. Sprinkle with ½ cup of cheese, then top with the remaining sliced chicken, the remaining onion and chorizo.
Drizzle with 1 tbsp barbecue sauce and bake for 15-20 mins, until the cheese is melted and the meat has started to brown. Sprinkle with freshly chopped parsley to garnish.
Serving Size 6