Pre-heat your oven to 180°C/350°F

Start by preparing the vegan mince filling. In a medium-sized frying pan, add 1 tbsp of the cooking oil on medium heat, then sauté the diced onion for 3 minutes or so until fragrant.

Crumble in the mince and stir-fry before adding in the garlic, chopped tomatoes tomato paste and water. Stir everything to combine well, season with salt and pepper then leave to simmer on a medium-low heat for 5-10 minutes until the mixture reduces - you don't want it to be too watery.

In a shallow wok or frying pan, sauté the marrow slices stirring frequently until browned (for about 8 minutes).

Now for the bechamel - whisk together the flour, soy milk and season with sea salt and black pepper then add to a small saucepan on medium heat. Stir frequently until thickened, scraping down the edges with a rubber spatula as needed.

In an 8-inch casserole dish, layer the mince mixture, followed by the marrow slices and finally the bechamel on top.

Bake for 25 minutes along with an extra 3-5 minutes on the broiler to brown as necessary - if you're using cheese add it on top during the last 5 mins of cooking.