Boil the potatoes until tender, then drain. Add butter and season to taste with pepper and salt, then mash until very smooth. Add egg white and mix until well combined. Stand covered for about 15 minutes.
Place teaspoonfuls of potato mixture onto well-greased non-stick oven trays, spreading thinly with a spatula to make discs about 6cm in diameter.
Bake at 180°C for about 18-20 minutes or until golden and crisp. Cool on a cake rack.
Combine yoghurt, lime juice, chilli, chives and parsley. Spoon a teaspoon on top of each wafer. Top with Kingfish, a few chives and a drop or two of lime juice.
Potato wafers can be made 2-3 days ahead and stored in an airtight container at room temperature. Crisp for a few minutes in a moderate oven before assembling [if necessary].
Makes approx 24.