Heat olive oil in a large skillet over medium heat. Add diced onion and sauté until translucent, about 5 minutes.

Stir in minced garlic and cook for an additional minute until fragrant.

Add ground turkey or beef to the skillet, breaking it apart with a spoon. Cook until browned, about 6-8 minutes.

Stir in red pepper flakes and Italian seasoning, then add crushed tomatoes and sugar. Season with salt and pepper to taste. Let the mixture simmer for 15-20 minutes, stirring occasionally.

While the sauce simmers, bring a large pot of salted water to a boil. Cook the jumbo pasta shells according to package instructions until al dente, about 10-12 minutes. Drain and set aside.

In a medium bowl, combine ricotta cheese, grated Parmesan cheese, and heavy cream. Whip until smooth and creamy.

To assemble, spread half of the meat sauce in the bottom of a large baking dish.

Fill each pasta shell with a generous dollop of the whipped ricotta mixture and place them in the baking dish. Top with the remaining meat sauce.

Preheat the oven to 375°F. Bake the assembled dish for 20-25 minutes until bubbly and heated through.

Garnish with fresh basil leaves before serving.