Step 1

Preheat oven to 350 degrees F (175 degrees C). Lightly oil a 9x13 baking dish.

Step 2

Bring a large pot of lightly salted water to a boil. Cook shells in the boiling water, stirring occasionally until tender yet firm to the bite, about 10 to 12 minutes. Drain. Lightly oil a rimmed baking sheet; place drained pasta on baking sheet to cool.

Step 3

Heat 2 teaspoons vegetable oil over medium-high heat in a heavy skillet. Cook and crumble sausage until it has lost its pink color and begins to brown. Remove from heat; drain off grease.

Step 4

Stir half of the shredded cheese and the Italian seasoning into the browned sausage. Spoon mixture into the pasta shells (1 to 2 tablespoons per shell). Arrange stuffed shells in prepared baking dish. Pour marinara sauce evenly over the shells. Top with remaining shredded cheese. Cover tightly with aluminum foil.

Step 5

Bake in preheated oven until heated through and bubbly, about 30 minutes. Remove foil; bake until browned, 5 to 10 more minutes. Sprinkle with a pinch of Italian seasoning, if desired.