1 Place the lamb, egg, mustard, dill, lemon zest and crushed crackers in a bowl. Season well with salt and pepper. Mix till combined.
2 Divide the meat mixture in four, shape into balls and flatten each one with the palm of your hand. Place a little block of feta into the centre of each then gather up the sides and fold the mince mixture over the cheese to ensure it's enclosed.
3 Leave the burgers to rest in the fridge for 10 minutes before cooking on barbecue, or frying pan or griddle. Serve in the toasted brioche buns right away once cooked, so that the cheese is still soft inside.