Step 1

Place the chicken, ricotta, milk, spring onion and tarragon in a food processor and season with salt and pepper. Pulse briefly until the chicken is evenly minced - don't overmix. Using damp hands, form the mixture into 8 small patties (about 2cm thick), then chill for 10 minutes.

Step 2

Meanwhile, combine the yoghurt with the mustard in a bowl and season.

Step 3

Heat a large non-stick frypan over high heat. Spray with oil, reduce heat to medium, then cook the patties, in batches if necessary, for 4-5 minutes each side until browned and cooked through.

Step 4

To assemble the burgers, fill each roll with salad leaves, tomato, 2 burger patties and yoghurt. Serve immediately.