Creating this dish involves a series of simple steps. Here’s how to prepare the Creamy Spinach and Beef Cannelloni:

Step 1: Prepare the Filling

1. In a large skillet over medium heat, cook the ground beef until browned. Drain excess fat.
2. Add minced garlic and chopped spinach to the skillet. Sauté until the spinach wilts.
3. Remove from heat and let the mixture cool slightly.
4. In a large mixing bowl, combine the beef and spinach mixture with ricotta cheese, mozzarella, Parmesan, egg, oregano, salt, and pepper. Mix until well combined.

Step 2: Prepare the Cream Sauce

1. In a saucepan, melt butter over medium heat.
2. Stir in flour and cook for about 1 minute, until it forms a smooth paste.
3. Gradually add milk, whisking continuously to prevent lumps.
4. Add nutmeg, salt, and pepper. Cook until the sauce thickens, about 5-7 minutes. Remove from heat.

Step 3: Assemble the Cannelloni

1. Preheat the oven to 375°F (190°C).
2. If using lasagna sheets, boil them according to package instructions until al dente. Drain and let cool slightly.
3. Spread a thin layer of the cream sauce at the bottom of a baking dish.
4. Fill each cannelloni tube with the beef and spinach mixture. If using lasagna sheets, place filling along one edge and roll up.
5. Arrange filled cannelloni in the baking dish.

Step 4: Bake the Cannelloni

1. Pour the remaining cream sauce over the cannelloni, ensuring even coverage.
2. Cover the dish with aluminum foil.
3. Bake in the preheated oven for 25 minutes.
4. Remove foil and bake for an additional 10 minutes, or until the top is golden and bubbly.

Step 5: Serve

1. Let the cannelloni cool for a few minutes before serving.
2. Optionally, heat marinara sauce and serve it alongside or drizzled over the cannelloni.
3. Garnish with fresh basil or parsley for a pop of color.