Mince the onion and microwave it for 1 minute at 600W, then let it cool. Slice zucchini into 1cm rounds and cut red bell pepper into 2cm squares.

Divide the pizza cheese into two portions and shape them into balls.

In a bowl, soak breadcrumbs in milk, then add the remaining hamburger mixture ingredients and mix until sticky. Divide the mixture into two portions and shape into patties, inserting the cheese inside.

Heat salad oil in a pan and sear the patties on both sides until browned. Remove and place them in a heatproof dish. Prepare the demi sauce by combining all ingredients except butter, simmer until thickened, then stir in butter.

Arrange zucchini, pumpkin, and red bell pepper around the patties in the dish. Bake in a preheated oven at 220°C for 10–12 minutes until cooked through.