Steam the cauliflower florets in a pot for about 10 minutes until tender. Once cooked, transfer them to a blender, add vegetable broth, milk, garlic, Italian seasoning, salt, and pepper. Blend until smooth and creamy. Adjust seasoning to taste.
In a large mixing bowl, combine the ricotta cheese with 1 cup of shredded mozzarella and half of the grated Parmesan. Mix until well combined.
Cook the lasagna noodles according to the package instructions until al dente, then drain and set aside.
In an 8x12-inch baking dish, spread a thin layer of the creamy cauliflower sauce at the bottom.
Layer 3 lasagna noodles on top. Spread half of the ricotta mixture over the noodles, followed by a handful of fresh spinach. Add another layer of the cauliflower sauce over this.
Repeat the layering: noodles, ricotta mixture, spinach, and sauce. Finish with a top layer of noodles.
Pour the remaining cauliflower sauce over the final layer and sprinkle with the rest of the mozzarella and Parmesan cheese.
Cover the dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 15-20 minutes or until the top is bubbly and golden brown.
Let the lasagna cool for about 10 minutes before slicing to allow it to set.
Notes
Garnish with fresh basil leaves and additional Parmesan cheese before serving.