Blue-rocket burgers Recipe | Food Network UK

Ingredients

• 2 Tbsp extra-virgin olive oil, divided
• 2 Tbsp butter
• 1 large onion, sliced
• Salt and freshly ground black pepper
• 1 Tbsp brown sugar
• splash water
• 50ml spicy brown mustard
• 680g beef mince
• 2 cloves garlic, grated
• 3 Tbsp Worcestershire sauce, eyeball it
• A handful of fresh parsley, finely chopped
• 225g blue cheese, thinly sliced
• 4 crusty rolls, split, lightly toasted
• 2 handfuls rocket leaves, coarsely chopped