01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish.
02 - Cook jumbo pasta shells in salted boiling water until al dente per package directions. Drain and set aside.
03 - In a large skillet over medium heat, brown ground beef. Add onion and garlic, sauté 2-3 minutes until softened. Season with Italian herbs, salt, and pepper. Remove from heat and cool slightly.
04 - In a large bowl, combine ricotta cheese, egg, Parmesan, 1 cup mozzarella, and parsley. Fold in cooled beef mixture until blended.
05 - Mix marinara sauce and heavy cream in a separate bowl. Spoon half the sauce mixture into the prepared baking dish.
06 - Fill each pasta shell with approximately 2 tablespoons of the beef-ricotta mixture. Arrange stuffed shells in the baking dish.
07 - Pour remaining sauce evenly over stuffed shells. Sprinkle with 1/2 cup mozzarella and 2 tbsp Parmesan.
08 - Cover dish with foil and bake for 25 minutes.
09 - Remove foil and bake uncovered for 10 minutes until cheese is bubbly and golden.
10 - Let rest 5 minutes before serving. Garnish with extra parsley if desired.