Heat a large skillet over medium-high heat with olive oil. Add ground beef and Italian sausage, then use a spatula to break up into small pieces. Cook then add chopped garlic, dried oregano, Kosher salt, and crushed red pepper flakes. Stir well.
Add marinara sauce, chicken stock, and a generous handful of fresh basil leaves. Stir well, then bring the sauce to a simmer.
Lower the temperature slightly, cover the pan with a lid or foil, then cook, stirring occasionally, until the noodles are al dente. Keep an eye on the liquid. Add an additional ½ cup chicken stock.
In a small bowl, whisk together ricotta, grated Parmesan, large egg yolk, Kosher salt, and black pepper.
Once the noodles are al dente, dollop the ricotta mixture all over the top of the lasagna skillet. Sprinkle with shredded mozzarella.
Transfer the skillet lasagna under a broiler set to high, then cook until the cheese is golden brown, bubbling, and melted. Allow to cool slightly, then top with additional fresh basil and chopped fresh parsley.