1. Preheat oven to 400°.
2. Cook pasta 7 minutes or until almost al dente, omitting salt and fat. Drain well.
3. Heat a medium skillet over medium heat. Add oil to pan; swirl to coat. Add shallots; cook 4 minutes, stirring occasionally. Add garlic; cook 1 minute, stirring constantly. Add cream cheese, milk, and pepper; cook until cheese melts, stirring until smooth. Remove from heat. Stir in basil. Place shrimp in a bowl. Sprinkle with potato starch; toss well to coat. Add cream cheese mixture to shrimp; toss well.
4. Divide shrimp mixture evenly among pasta shells. Coat a 13 x 9-inch glass or ceramic baking dish with cooking spray; spread 1 cup marinara over bottom of dish. Arrange shells in prepared dish; top with remaining 2 cups marinara. Sprinkle shells evenly with Parmigiano-Reggiano cheese. Bake at 400° for 30 minutes or until shrimp is done.