Instructions

In a saucepan of boiling water, cook potatoes in their skins until tender; drain. When cool enough to handle, remove skins, slice potatoes thickly, or quarter. Put into a bowl and toss with olive oil.
Remove skin from mackerel and discard. Break fish into pieces and add to potatoes. Cut cucumber in half crosswise; dice one half and add to salad.
To make the dressing, mix ingredients together in a bowl or screw- top jar. Stir into the salad, then spoon onto a serving dish. Using an apple corer, remove centre from remaining piece of cucumber and discard. Slice cucumber. Serve the salad garnished with cucumber slices and parsley.