Bring a large pot of salted water to a boil and cook the tortellini according to package directions until al dente. Reserve 1/2 cup pasta water, then drain and set aside.

While the pasta cooks, season the sliced steak generously with salt and pepper.

Heat a large skillet over medium-high heat and add 1 tablespoon butter. When the butter shimmers, add the steak in a single layer and sear for 1–2 minutes per side until browned but not overcooked. Remove steak to a plate and tent with foil.

In the same skillet, lower heat to medium and add the remaining 3 tablespoons butter. Toss in the cracked garlic; it will sizzle and release a toasty, nutty aroma. Cook until the edges brown, about 1 minute — watch carefully so it does not burn. Remove the garlic if you prefer only its infused flavor, or leave it for texture.

Add the chopped shallot and cook until translucent, scraping up any browned bits from the steak. Pour in the beef broth and simmer for 1–2 minutes to reduce slightly.

Stir in the heavy cream and Dijon mustard, bringing the mixture to a gentle simmer. The sauce will thicken and coat the back of a spoon.

Add the grated Parmesan and Italian seasoning, stirring until the cheese melts into a glossy sauce. Adjust seasoning with salt and pepper. If the sauce is too thick, whisk in reserved pasta water a tablespoon at a time.

Return the sliced steak to the skillet along with cooked tortellini and any optional vegetables like spinach or roasted tomatoes. Toss gently to coat everything in the sauce and warm through for 1–2 minutes.

Plate with a shower of fresh parsley or basil and an extra grating of Parmesan. Serve immediately.