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