Polish Zapiekanki

Steps

1. Preheat your oven to 200°C (180°C fan) or gas mark 6. Place the baguettes on a baking tray and bake for 8-10 minutes, then let them cool.
2. In a pan, heat 2 teaspoons of butter and 1 teaspoon of vegetable oil over low heat. Add the chopped onion and sauté for 5 minutes until softened. Incorporate the mushrooms and increase the heat to medium, cooking for another 5-10 minutes until the vegetables are tender and the mushroom liquid has evaporated. Add in the garlic and cook for an additional 1-2 minutes. Season to taste, then mix in the mayonnaise and remove from heat.
3. Slice the cooled baguettes in half lengthwise and return them to the baking tray, cut-side up. Spread the mushroom mixture on top, then sprinkle with cheddar cheese, ham, Polish kabanos, and mozzarella. Bake for another 8-10 minutes, or until the cheese is melted and golden brown.
4. Meanwhile, in a separate pan, heat the remaining butter and oil over medium heat. Fry the sliced onions for about 5 minutes until they are golden and soft. Set aside. Once the zapiekanki are ready, top them with the caramelized onions, dill pickles (if desired), chives, and a drizzle of ketchup.