Hearty Mushroom & Leek Lasagne

• In a large frying pan, heat a generous drizzle of olive oil over high heat. Cook mushrooms, stirring, until tender, 8-10 minutes.
• Add half the garlic and cook until fragrant, 1 minute. Season with salt and pepper. Transfer to a small bowl and set aside.
• Return the frying pan to medium-high heat, with a drizzle of olive oil. Cook onion, sliced leek and carrot, stirring, until softened, 6-7 minutes.
• Add Nan's special seasoning and remaining garlic and cook until fragrant, 1-2 minutes. 

• Reduce heat to medium, then add vegetable stock powder, passata, the brown sugar, salt, butter and water and cook until thickened, 1-2 minutes. Season to taste.
• Season with pepper. Stir through baby leaves until wilted. 

• Heat a medium saucepan over medium heat with a drizzle of olive oil. Cook the plain flour, stirring, until a thick paste forms, 2 minutes.
• Remove pan from heat, then slowly whisk in the milk until smooth.
• Stir through grated Parmesan cheese, then season to taste. 

• Spoon half the veggie mixture into a medium baking dish. Top with a lasagne sheet (lay two sheets alongside each other for 4 people).
• Repeat with the remaining veggie mixture and lasagne sheets.
• Arrange garlicky mushrooms in a single layer on top of lasagne. Using the back of a spoon, spread the white sauce over mushrooms.
• Bake lasagne until golden, 20-25 minutes.