01 - Preheat oven to 400°F.
02 - Slice the tops off the garlic bulbs to expose the cloves. Drizzle with 1 tbsp olive oil, wrap in foil, and roast for 30 minutes until soft and golden.
03 - Pat the flank steak dry. Rub with 1 tbsp olive oil, salt, and pepper.
04 - Heat a large ovenproof skillet over medium-high heat. Sear the steak for 3–4 minutes per side until well browned. Transfer skillet to oven and roast for 6–8 minutes for medium-rare, or adjust for desired doneness.
05 - Remove steak from oven, transfer to a plate, and tent loosely with foil. Let rest for 10 minutes.
06 - Squeeze roasted garlic cloves from bulbs into a small saucepan. Add broth and bring to a simmer over medium heat, whisking to break up garlic.
07 - Add cream, butter, Dijon mustard, and lemon juice. Simmer gently for 2–3 minutes, whisking until smooth and slightly thickened. Season with salt and pepper to taste.
08 - Slice flank steak thinly across the grain. Spoon roasted garlic sauce over steak. Garnish with fresh parsley if desired.