Preheat the grill to high.
Whisk the honey and mustard together. Place the mackerel onto the baking tray, skin-side down, and brush with the honey mixture.
Grill for two minutes on each side. Set aside to rest.
Meanwhile, toast the bread under the grill until lightly browned. Slice though the middle of the bread, horizontally. With the cut, untoasted side facing upwards slice the bread into 1cm/½in strips. Grill the untoasted side of the bread slices until golden-brown.
Place the avocados into a bowl with the chives, lime juice and olive oil. Mix together until well combined and season with salt and freshly ground black pepper.
Place the avocado mixture into a chefs' ring, leaving a gap on top. Spoon over the double cream and level with a palate knife. Remove the chef’s ring.
Scatter over the coriander cress and serve alongside the mackerel and melba toast.