Steak Out: Drunken Onion Gravy over Sliced Steak with Mashed Potatoes – Rachael Ray

Ingredients

• 3 tablespoons butter
• 4 medium onions, sliced
• Salt and pepper
• 2 tablespoons flour
• 1 bottle dark beer, such as Guinness
• 1 tablespoon Worcestershire sauce
• 1 cup beef stock
• 2 pounds potatoes
• Whole milk or half-and-half, for mashing
• 2 tablespoons Dijon mustard
• Grated nutmeg
• 1 small bundle farm spinach, stemmed and chopped
• 4 flat-iron steaks or 2 pounds flank steak
• Oil, for drizzling