Preheat the oven to 350°F.
Bring a large pot of water (about 4 quarts) to a rolling boil. Add 1 tablespoon of table salt to season the water for the pasta.
Carefully add the pastato the boiling water, stirring gently to prevent sticking. Follow the cookingtime specified on the pasta package (usually around 9 minutes).
Using a colander orstrainer, drain the pasta to remove all the water. Set the drained jumbo pastashells aside.
Meanwhile, prepare thechicken filling by combining the ingredients: chicken, ricotta cheese, parmesancheese, mozzarella cheese, sour cream, Italian seasonings, black pepper, andsalt. Mix until well combined.
Stuff the shells withthe prepared chicken mixture and set them aside.
Heat a skillet overmedium heat, melt the butter, and add minced garlic. Cook for a minute.
Stir in the heavy creamand cook for 2 minutes.
Add the parmesan cheese,Italian seasonings, salt, pepper, and crushed red pepper flakes. Let it simmerfor 4-5 minutes until the sauce slightly thickens.
Pour the sauce over thebaking dish, arrange the stuffed pasta shells, and sprinkle mozzarella cheeseon top.
Bake the stuffed shellsfor 18-20 minutes until the cheese has melted.
Garnish the pasta withparsley and red pepper flakes before serving.