Smashed Beef Burgers

Ingredients

• 600g good quality beef mince
• 1 Tbsp olive oil
• ½ Tbsp Worcestershire sauce
• 1 beef stock cube, crumbled
• ½ tsp salt
• ¼ tsp cracked pepper
• 1 Tbsp butter
• 1 large brown onion, thinly sliced
• 2 tsp balsamic vinegar
• 2 tsp brown sugar
• 4 Freya’s Brioche Style Buns
• Burger sauce
• Butter lettuce leaves
• Sliced tomato
• Sliced cheddar cheese
• Whole gherkins