Begin by bringing a large pot of salted water to a boil. Add your chosen pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain the pasta and set aside.

Heat olive oil in a large skillet over medium-high heat. Add the steak pieces and sear for 3-4 minutes until browned. Remove the steak from the skillet and set aside.

In the same skillet, add the diced onion and sauté for 2-3 minutes until translucent. Stir in the minced garlic and cook for an additional 30 seconds.

Reduce the heat to low and pour in the heavy cream, stirring gently. Gradually add the shredded truffle Gouda and mozzarella cheese, mixing until melted. Season with salt, black pepper, and optional red pepper flakes.

Return the seared steak to the skillet and add the drained pasta. Toss gently until everything is well-coated with the sauce.

Preheat your oven to 375°F (190°C). Grease a baking dish and transfer the pasta mixture to the dish. Bake uncovered for 15-20 minutes or until golden and bubbly.

Allow the dish to rest for about 5 minutes, then garnish with freshly chopped parsley before serving.