Brown the meat. Heat a large skillet over medium-high heat with 1 Tbsp olive oil. Add ½ lb ground beef and ½ lb Italian sausage, then use a spatula to break up into small pieces. Cook for 3-4 minutes, then add chopped garlic, 2 tsp dried oregano, 1 tsp Kosher salt, and ¼ tsp crushed red pepper flakes. Stir well.
Make the sauce. Add 4 cups marinara sauce, 1 cup of chicken stock, and a generous handful of fresh basil leaves. Stir well, then bring the sauce to a simmer.
Add the broken lasagna noodles, then stir well to ensure the noodles are covered with sauce. Lower the temperature slightly, cover the pan with a lid or foil, then cook, stirring occasionally, until the noodles are al dente, about 20-25 minutes. Keep an eye on the liquid, as a lot of it will be absorbed by the noodles. Add an additional ½ cup chicken stock, as needed.
Make the ricotta mixture. In a small bowl, whisk together 1½ cups ricotta, ½ cup grated Parmesan, 1 large egg yolk, ½ tsp Kosher salt, and ¼ tsp black pepper.
Add the cheese. Once the noodles are al dente, dollop the ricotta mixture all over the top of the lasagna skillet. Sprinkle with 1½ cups shredded mozzarella.
Broil until the cheese melts. Transfer the skillet lasagna under a broiler set to high, then cook for 3-5 minutes (depending on the strength of your broiler, keep a close eye on it!) until the cheese is golden brown, bubbling, and melted. Allow to cool slightly, then top with additional fresh basil and chopped fresh parsley.