Ingredients

1½ tbsp olive oil

1 onion, very finely chopped

70g smoked pancetta, finely chopped

1 garlic clove, crushed

4 thyme sprigs, leaves picked

500g lean beef mince (no more than 10% fat)

50g freshbreadcrumbs

1 egg yolk

60g mature cheddar, grated

60g grated mozzarella

120g mayonnaise

2½ tsp English mustard

½ small bunch of parsley, finely chopped

½ small bunch of basil

50g baby gherkins, finely chopped

4 seeded burger buns, split

2-3 Little Gem lettuces, leaves separated

2 ripe tomatoes, sliced

Crispy fried onions

Instructions

Step 1: Heat the olive oil in a frying pan over medium heat. Add the finely chopped onion with a pinch of salt and cook gently for 15 minutes until soft and translucent.

Step 2: Add the chopped pancetta and cook for another 5 minutes. Then add the crushed garlic and thyme leaves and cook for 2 more minutes. Remove the pan from heat and let the mixture cool for 15 minutes.

Step 3: Place the mince in a large bowl and massage with your hands for about 5 minutes to tenderise the meat. Add the cooled onion mixture, fresh breadcrumbs, and egg yolk. Season generously with salt and pepper. Divide into four equal portions and gently mix.

Step 4: Combine the grated cheddar and mozzarella. Form each beef portion into a 10cm round patty. Divide the cheese mixture into four balls and flatten each into a 4cm disc.

Step 5: Place a cheese disc in the center of each patty and fold the meat around it completely, sealing the cheese inside. Lightly pat each burger to flatten slightly. Cover and chill for at least 30 minutes, up to 48 hours.

Step 6: To make the sauce, blend the mayonnaise, English mustard, parsley, and basil in a small food processor. Stir in the chopped gherkins, then cover and chill until ready to serve.

Step 7: Preheat your barbecue. Once the flames have died down, grill the burgers for 4-5 minutes on each side until charred and cooked through. Wrap each burger in foil and leave on the barbecue for 5-7 minutes to melt the cheese inside.

Step 8: Grill the burger buns cut-side down for 1-2 minutes until toasted. Spread the sauce on all the cut sides, then assemble the burgers with lettuce, tomato slices, and crispy fried onions. Serve immediately.

Tips & Variations

If you don’t have a barbecue, cook the burgers in a lightly oiled frying pan over medium heat for 4-5 minutes per side until golden. Then transfer to a baking sheet and bake at 220°C (200°C fan/gas 8) for 10 minutes to melt the cheese center.

Try swapping smoked pancetta for diced bacon or omit for a vegetarian twist using plant-based mince and cheese alternatives.

For an extra kick, add a pinch of chili flakes to the beef mixture before shaping the patties.

FAQs

Can I prepare the burgers in advance?

Yes, you can prepare and assemble the burgers up to 48 hours ahead. Keep them covered and chilled until ready to cook.

How do I prevent the cheese from leaking out during cooking?

Make sure to seal the meat tightly around the cheese and chill the assembled burgers before cooking. Wrapping them in foil after initial grilling also helps the cheese melt without leaking.