Ultimate Radish Burger

For the pickled radish:

• 6 radishes, sliced
• 2 tbsp red wine vinegar
• 2 tbsp sugar

For the burgers:

• 1 onion, peeled and finely chopped
• 6 radishes, finely chopped
• Olive oil
• 500g beef mince
• Salt and pepper
• A handful of Parmesan cheese, grated
• 1 heaped tbsp Dijon mustard
• 1 large egg
• 100g breadcrumbs
• 4 burger buns

For the radish mayo:

• 100g mayonnaise
• Zest and juice of half a lemon
• 2 radishes, finely sliced
• Salt and pepper

To serve:

• Lettuce
• Fries