Preheat oven to 375 degrees F (190 degrees C).
Cook and drain Manicotti Noodles (8) according to package directions. Keep shells in cold water until ready to use.
While pasta is cooking, heat Extra-Virgin Olive Oil (1 tablespoon) over medium heat in a large skillet. Add in the Onion (2 tablespoon), cooking for 3 to 5 minutes. Add the Garlic (2 clove) and cook for about one minute.
Add in the sliced Mushroom (2 cup) and saute for 3 to 5 minutes more. Finally, add the Fresh Baby Spinach (2 cup) and allow to wilt for about 1 minute. Remove from heat and cool.
In a small bowl, mix together the Ricotta Cheese (16 ounce) and Parmesan Cheese (2 ounce), add to the slightly cooled mushroom mixture, and season with Salt and Pepper (to taste).
Mix Condensed Cream of Mushroom Soup (2 can) with Heavy Cream (1/2 cup), then pour half into the bottom of an 8-inch baking dish.
Using a small spoon, gently stuff each manicotti shell with 2 - 3 tablespoons of mushroom ricotta mixture and place in a single layer in the dish.
Pour the remaining soup and cream mixture over the top of the pasta shells, garnish with Parmesan Cheese (to taste) and Fresh Thyme (to taste) if desired, and bake in a 375 degrees F (190 degrees C) preheated oven for about 15 minutes or until bubbly.