Preheat your oven to 200°C (about 400°F). In a baking dish, toss the diced butternut squash with a drizzle of olive oil and a sprinkle of salt.

Roast for about 25 minutes or until the squash is tender and slightly caramelized. This roasting process really brings out that natural sweetness.

In a medium saucepan, melt 70 grams of butter over medium heat. Whisk in the plain flour, cooking for about a minute to create a roux. Gradually whisk in the semi-skimmed milk. Bring to a simmer, stirring frequently. Once thickened, add the mascarpone cheese and grated parmesan. Season with nutmeg, white pepper, and lemon zest for flavor.

In a skillet, heat a bit of olive oil over medium heat. Add the washed spinach and whole garlic cloves. Sauté until the spinach wilts. Remove from heat and let cool slightly. Once cooled, remove the garlic cloves and discard them.

In a large baking dish, pour a layer of white sauce on the bottom. Place a layer of lasagna sheets over the sauce. Next, add half of the roasted butternut squash, half the sautéed spinach, and half of the torn mozzarella. Spoon more white sauce on top.

Continue layering with another set of lasagna sheets, remaining butternut squash, spinach, and mozzarella. Finish with a final layer of lasagna sheets, the remaining white sauce, and sprinkle with grated parmesan.

Cover the baking dish with aluminum foil and bake in your preheated oven for about 30 minutes. Remove the foil and bake for an additional 15 minutes, or until the top is golden brown and bubbly. Let it cool for a few minutes before serving.