Stir in the marinara sauce and simmer, uncovered, for 5 minutes. Once slightly thickened, mix in the heavy cream and turn off the heat.
Whisk together the ricotta, egg, and basil pesto in a large bowl.
Spread 1 cup of the meat sauce in a 9x13 greased casserole dish. Top with 4 lasagna noodles, slightly overlapping. Next layer with ½ ricotta cheese mixture, 1 cup shredded mozzarella, and 1 cup meat sauce. Repeat these layers one more time. Finish with 4 noodles on top, remaining meat sauce, and remaining mozzarella. Then randomly place the fresh mozzarella pieces throughout the top.
Cover with foil that's been sprayed on the interior side with cooking spray, then bake for 45 minutes. Remove foil and bake for an additional 15 minutes, or until browned and bubbly. If desired, broil at the end for 2 minutes.
Allow the lasagna to rest for at least 10 - 15 minutes before cutting and serving. Garnish lasagna each lasagna slice with parmesan cheese, chopped parsley, and optional red pepper flakes.
Recipe by Slice of Jess at https://sliceofjess.com/classic-lasagna-recipe-3-generation-family-recipe/