Steak with cheesy Marmite and mushroom sauce - Southern Co-op

Ingredients

• 4 tsp olive oil
• 2 tsp butter
• 1 large onion, sliced
• 200g chestnut mushrooms, sliced
• 1 tbsp plain flour
• 300ml stout or other dark beer
• 2 tbsp Marmite
• 4 tsp Worcestershire sauce
• 2 x 227g packs British beef sirloin steak, trimmed of any fat
• 50g Cheddar, grated
• Steamed green beans and frozen fries, chips or wedges, to serve