Preheat oven to 375°F (190°C).

Bring a large pot of salted water to a boil.

Heat olive oil in a large skillet over medium-high heat.

Brown the sweet Italian sausage, breaking it into small pieces.

Add ground veal and brown, crumbling it as well.

Stir in sage, garlic, onion, salt, and pepper. Cook until the vegetables are tender.

Add defrosted and squeezed dry spinach to the skillet.

Heat spinach through, then deglaze the skillet with white wine. Remove from heat.

In a saucepot over medium heat, melt butter and whisk in flour until bubbly.

Gradually whisk in milk, seasoning with salt, pepper, and nutmeg.

Cook, whisking constantly, until the sauce thickens enough to coat the back of a spoon.

Remove a ladle of the sauce and whisk it into the lightly beaten egg yolks to temper them.

Pour the egg yolk mixture back into the sauce and stir in half of the fontina cheese and half of the Parmigiano-Reggiano.

Reduce heat to low or cover to keep warm.

Cook the cannelloni pasta or shells in the boiling water until al dente (about 6-7 minutes).

Drain the pasta and let it cool slightly.

Fill each cannelloni tube or shell with the meat filling using a small spoon.

Spread one-quarter of the cheese sauce on the bottom of a baking dish.

Arrange the filled cannelloni or shells over the sauce.

Cover the pasta with the remaining cheese sauce.

Sprinkle the remaining fontina and Parmigiano-Reggiano cheese over the top.

Bake at 375°F (190°C) for 30-40 minutes, or until golden brown and bubbly.