Dab matjes. Peel the onion. Wash, quarter and core the apple. Dice the matie, onion and apple very finely. Drain capers and chop finely.
Mix the matie, onion, apple and capers. Season to taste with vinegar, pepper and a little salt. Leave to stand for about 30 minutes.
Wash lettuce leaves, shake dry and pluck into pieces. Mix cream cheese and horseradish. Season with salt and pepper. Spread pumpernickel with cream cheese. Spread lettuce and matie satay on top.
Garnish with chives.