Meanwhile, heat one tablespoon of olive oil in a large pan. Add the chopped onion, carrot, and celery, and soften for 10-12 minutes on a low heat, stirring occasionally. Sprinkle in some salt and pepper at this stage.
After 10-12 mins, add the chopped garlic and chopped mushrooms and cook for 3-4 mins.
Next, add in the meat-free mince and cook for another 3-4 mins. If using frozen/fresh mince, simply throw it in and break it apart. If using dried mince, you'll first need to rehydrate it according to package instructions.
Once the mince has cooked for a few minutes, stir in the tomato puree. Cook for a couple of minutes before adding the tinned tomatoes, crumbled vegan stock cube/powder, Henderson's Relish, Marmite, bay leaves, dried oregano/mixed herbs, and some more salt and pepper. You can also rinse each tomato tin with a splash of water and add this to the pan.
Break the tomatoes apart with a spoon, then reduce the heat and cook for 20 minutes, stirring occasionally. The sauce should become quite thick. After around 20 minutes, turn off the heat and stir through the chopped basil. Remove the bay leaves and set aside.