Portobello Bun Burger | KARAN BEEF

Ingredients

• 750g minced beef
• 1 small red onion, finely chopped
• 2 garlic cloves, crushed
• 1/2 tsp origanum
• 1/2 tsp paprika
• 1 1/2 Tbsp wholegrain mustard
• 1 egg
• Salt and freshly ground black pepper
• Olive oil, for cooking
• 4 large Portobello mushrooms
• Toppings:
• 1 head/packet cos lettuce, leaves
• 2 tomatoes, thickly sliced
• 1/2 red onion, sliced into rings
• Wholegrain mustard
• Gherkins, for serving