Cook the lasagna sheets into salted boiling water according to package directions, then allow them to dry flat on a clean kitchen cloth.
In the meantime, mix ricotta and canned pumpkin to get a smooth cream, add a little water if needed; season with salt, pepper and thyme to taste.
Roast walnuts in a hot pan until slightly golden and set aside.
To assemble, spread a little pumpkin ricotta cream in the bottom of a baking dish. Arrange some lasagna sheets over it and spread well with pumpkin cream again. Top with some roasted walnut and basil leaves.
Repeat layers until you finish the lasagna sheets and pumpkin cream, end with roasted walnuts and sprinkle with breadcrumbs: they will form a nice crispy crust.