Step 2) Heat 2 teaspoons oil in a large skillet over medium heat; add shallots and sauté 3 to 5 minutes. Add remaining oil and mushrooms. Sauté an additional 5 to 7 minutes. Season with thyme, garlic powder, salt and pepper. Add sherry.
Step 3) Remove from heat. Stir in spinach and Dijon mustard; cool. Process mushroom/spinach mixture in food processor to a fine mince; set aside.
Step 4) Heat water in a large stockpot to a rolling boil. Add lasagna sheets and boil for 3 minutes. Remove lasagna sheets carefully from stockpot and place immediately in a bowl of ice water to cool down.
Step 5) Stir together marinara sauce and ricotta cheese; set aside.
Step 6) Remove lasagna sheets from ice water and pat dry with paper toweling. Cut each sheet in half creating 12 squares.
To Assemble:
Step 1) Spread 1/4 cup marinara sauce in the bottom of a greased 8 x 8-inch baking dish prepared with nonstick cooking spray. Place approximately 1 tablespoon mushroom spinach filling on one pasta square. Roll up and place seam side down in baking dish. Repeat with remaining filling and lasagna squares.
Step 2) Sprinkle any remaining mushroom/spinach mixture over top of cannelloni. Pour remaining sauce over cannelloni; bake for 20 minutes or until heated through. Sprinkle top with parmesan cheese.