Cook chicken breasts on a hot grill or BBQ for 3.5 minutes on one side or until circumference becomes white. Turn over and cook for a further 1.5 minutes. Meanwhile cook bacon and lightly toast wholemeal buns under the grill.
Spread high quality tomato relish to the edge of the bottom side of the bun. Layer cos lettuce, slices of fresh tomato & 4 thin slices of spanish onion on each burger.
While hot, place chicken and bacon on top of salad. Spread herb mayonnaise on crown of bun to edge.
Layer avocado on top of herb mayonnaise. Sprinkle with salt and pepper to taste.