Step 1

Preheat the oven to 350°F.

Step 2

Bring a large pot of salted water to a boil. Cook the jumbo shells according to package directions (there should be a set of instructions for cooking them for a shorter time, if they will be baked later. If not, cook them for 3 minutes less than the full cooking time). Drain the shells and rinse them with cold water in a colander or strainer. Set aside.

Step 3

Beat the egg in a large bowl. Add the spinach, ricotta, fontina, 1/4 cup whole milk, and oregano, season with salt and pepper, and stir to combine well.

Step 4

Melt the butter in a medium heavy saucepan over medium heat. Add the garlic and sauté for 1 minute, until golden. Add the half-and-half and the remaining 1/2 cup milk, and stir often until the mixture just starts to come to a simmer. Turn the head to low, and add the gouda a handful at a time, stirring just until each batch is melted. Stir in the red pepper flakes, season with salt and pepper, and remove from the heat.

Step 5

Spoon a thin layer of the gouda cheese sauce into the bottom of a shallow 3-quart baking dish (a 9x13-inch pan works well). Use a spoon or your fingers to stuff the cooked shells with the spinach-ricotta mixture, dividing it evenly between the shells. Line them up neatly in the prepared pan, following the shape of the pan. Give the gouda cheese sauce another good stir, then pour it slowly and evenly over the stuffed shells.

Step 6

Cover the pan with foil and bake for 30 minutes. Uncover the pan, turn the heat up to 475°F and continue to bake for about another 10 minutes, until the top turns golden brown and everything is lovely and bubbling. Let sit for 5 to 10 minutes before serving. Sprinkle with the basil, if desired, before serving.