Put the mince into a bowl. Add the mustard, garlic, onion and Worcester sauce. Season with salt and black pepper.
Mash roughly together the Stilton and chives, add half of this to the minced meat.
Combine the mixture well, then divide into 4 equal portions. Shape these into balls then flatten them between your palms.
Using your finger make a groove in each burger and put a teaspoonful of Stilton in each hole, then cover up with mince .
Put the burgers on a plate. Chill for about 30 minutes or until you're ready to cook.
Preheat your BBQ, grill or griddle pan. Lightly brush both sides of the burgers with some oil. Barbecue or fry for 4-5 minutes on each side, depending on how well cooked you like beef.
Cut the buns in half and toast them on the barbecue or grill, cut-side down, until slightly charred.
Assemble the burger to your liking: layer lettuce, sliced tomatoes, onion, gherkin and tomato ketchup on the bottom half of the bun, place the burger on top, then cover with the other half of the bun.