Heat olive oil in a large oven-safe pan over medium heat. Add sausage and cook, breaking it apart, until golden and browned.
Add leek, garlic and sage and cook for 3–4 minutes until softened and fragrant.
Stir through zucchini and cook for a further 2–3 minutes until slightly tender.
Pour in vegetable stock, Creamy One-Pot Recipe Base, cream, Dijon mustard and pepper. Stir well to combine.
Break lasagne sheets into pieces and stir through the sauce, ensuring they are mostly submerged in the liquid.
Simmer for 8–10 minutes, stirring occasionally, until the pasta begins to soften. Add a splash of water if needed.
Stir through spinach until wilted, then sprinkle over parmesan.
Transfer to a preheated 180°C oven for 15 minutes, then finish under the grill for 2–3 minutes until golden and bubbling.
