Preheat the oven to 375°F (190°C).
In a bowl, mix ricotta cheese, egg, garlic, and half of the Parmesan cheese. Season with salt, pepper, and thyme.
Spread 1/3 of the butternut squash puree on the bottom of a baking dish.
Layer 3 lasagna noodles over the puree, followed by half of the ricotta mixture.
On top of the ricotta, add another third of the butternut squash puree and a third of the mozzarella cheese.
Repeat the layering process with another 3 noodles, the remaining ricotta mixture, another third of the squash puree, and more mozzarella.
Top with the final 3 noodles, the remaining squash puree, mozzarella, and the rest of the Parmesan cheese.
Cover the dish with aluminum foil and bake for 30 minutes, then remove foil and bake for another 15-20 minutes until bubbly.
Let the lasagna rest for 10-15 minutes before serving.