Preheat your oven to 400°F (200°C). Toss broccoli with olive oil, garlic powder, salt, pepper, and balsamic vinegar if using. Roast for 20–25 minutes until crispy edges form.
Heat a tablespoon of olive oil in a skillet over medium-high heat. Season steak strips with salt, pepper, and garlic powder, then sear for 2–3 minutes per side until browned. Remove and set aside.
Boil a large pot of salted water and cook pasta until al dente. Reserve 1 cup of pasta water before draining to adjust sauce consistency later.
Melt butter in the same skillet, sauté onion until soft, then add minced garlic for 30 seconds. Pour in heavy cream and beef broth, simmer for 3–4 minutes, then stir in crumbled blue cheese until smooth. Adjust seasoning with salt and pepper.
Toss pasta in the sauce, add steak, and gently mix. Add reserved pasta water if needed for a creamier texture. Plate with roasted broccoli and garnish with fresh parsley.