Preheat oven to 400 degrees.
Bring a large pot of salted water to a boil and cook pasta shells for 7 minutes, or until almost al dente. Drain well.
Heat oil in a medium skillet over medium heat. Add shallots, cook 3-4 minutes, stirring occasionally.
Stir in garlic, cook 1 minute, stirring constantly.
Add cream cheese, milk, and pepper, cook, stirring, until cheese melts and mixture is smooth. Remove from heat and stir in basil.
Place shrimp in a large bowl and sprinkle with cornstarch. Toss to coat.
Add cream cheese mixture to shrimp, toss well.
Divide shrimp mixture evenly among pasta shells.
Coat a 13x9-inch glass or ceramic baking dish with cooking spray.
Spread 1 cup marinara over bottom of dish.
Arrange stuffed shells over marinara, top with remaining 2 cups marinara.
Sprinkle with Parmesan.
Bake 25-30 minutes, or until shrimp is cooked.
