Boil the quails' eggs for 2½ minutes, or the medium eggs for 8 minutes, drain and run under cold water. Peel and halve (or grate the medium eggs). Stamp out 24 rounds from the rye bread with a 4cm cutter; spread each with mayonnaise. Top with tomato, a quails' egg half or some grated egg and a few chives. Finish with a grinding of black pepper and sea salt flakes.
Get ahead: cook the eggs, slice the tomatoes and stamp out the rye bread a few hours ahead.