Heat the olive oil in a deep, wide frying pan over a medium heat. Crumble in the sausage meat and fry for 5 minutes until browned. Stir in the cannellini beans, lightly mashing some for texture. Transfer the mixture to a bowl and set aside.

Lower the heat. To the same pan, add the shallots and cook for 3–4 minutes until soft and lightly browned. Season with a pinch of salt. Add the garlic, chilli flakes and rosemary and fry for 30 seconds. Add the kale with a splash of stock and cook for 2 minutes until softened. Add the spinach and peas, then pour in the rest of the 450ml of stock.

Briefly bring to a simmer until the greens are just wilted and the peas are cooked. Don't overcook as you'll lose that vibrant green colour.

Blend until smooth (add more stock if needed for a pourable texture). Return to the pan with the sausage and bean mix and loosen with more stock if it's too thick.

Melt the butter in a saucepan over a medium–low heat, then stir in the flour and cook for 1 minute until it forms a paste. Take the pan off the heat and add around a third of the milk, whisking until smooth and lump-free. Gradually whisk in the remaining milk, then return the pan to the heat. Cook for another 6–7 minutes, until the sauce thickens and coats the back of a spoon, whisking constantly to avoid lumps. Stir in the Parmesan and nutmeg (if using), then season to taste with salt and pepper.

Preheat the oven to 200°C fan. Spread some of the green sauce into a medium baking dish (approx. 30 x 20cm and at least 6cm deep), then cover with lasagne sheets, béchamel and Parmesan. Repeat twice, ending with béchamel, then top with extra Parmesan.

Bake for 40–45 minutes until golden and bubbling. Leave to rest for 5–10 minutes before slicing and serving with a green side salad.