Heat the oven to 200C/180C fan/gas 6. Bake the baguettes on a baking tray for 8-10 mins, then leave to cool.

Heat 2 tsp of the butter and 1 tsp of the oil in a pan over a low heat and cook the chopped onion for 5 mins until soft. Stir in the mushrooms, turn the heat to medium and cook for 5-10 mins more until the veg is soft and the mushroom liquid has evaporated. Stir in the garlic and cook for 1-2 mins until soft. Season, then stir in the mayonnaise and remove from the heat.

Halve the baguettes lengthways, then return to the baking tray, cut-side up and spread over the mushroom mixture, then sprinkle over the cheddar, ham, kabanos and mozzarella. Bake for 8-10 mins, or until the cheese has melted and turned golden.

Meanwhile, heat the remaining butter and oil in a pan over a medium heat and fry the sliced onions for 5 mins until golden and soft. Remove from the heat and set aside. Once the pizzas are cooked, top with the caramelised onions, dill pickles (if using), the chives and a zig-zag drizzle of ketchup.