• Preheat the oven to 200 C / 400 F / gas mark 6.
• Slice the aubergines in half, lengthwise and cut a criss-cross pattern into the flesh being careful not to cut all the way down to the bottom.
• Place the aubergines into a baking tray and brush with a little olive oil before seasoning with salt and pepper.
• Roast the aubergines in the preheated oven for about 40 minutes or until the flesh is soft

Make the sauce:

• Heat the olive oil in a pan then add the onion and a pinch of salt.
• Cook over medium heat for 8 - 10 minutes until soft.
• Add the garlic and cook until it releases its aroma.
• Add the mushrooms and walnuts and cook until the water from the mushrooms has evaporated (roughly 15 minutes).
• Add the passata and cook the sauce over medium-high heat until thickened.
• Season with the herbs and spices.

Make the béchamel:

• Place the vegan butter in a saucepan and warm gently until melted.
• Add in the flour to create a roux and cook on a medium heat for 1 minute, stirring well to make sure it forms a smooth paste.
• Add the soy milk slowly making sure there are no lumps.
• Once the roux begins to get thin you can begin adding the milk faster.
• Once all the milk has been added bring to a simmer.
• Let it cook for another 5 minutes until thickened.
• When the sauce has thickened take the pan off the heat again and add in the grated vegan cheese.
• Keep stirring until the cheese has melted completely (add it back on to the heat if you need to).
• Finally, add in the remaining ingredients and stir until they are distributed throughout the sauce.

To assemble:

• Mash the aubergine flesh.
• Spoon over the mushroom sauce followed by the béchamel.
• Bake for 20 minutes or until golden brown on top.