Cut out 12 circles of bread to fit in a mini tartlet tin. Brush both sides of the bread with the melted butter, then press the rounds into the tin. Bake for 15 minutes.
Meanwhile, poach 12 quail eggs. Put 5cm (2inches) water in a small, deep frying pan. Bring to the boil, then lower the heat to very low. Crack each quail egg, one at a time, onto a large spoon. Hold the spoon on the surface of the water for 15 seconds until the egg white sets, then gently lower the spoon into the water, immersing the egg. Hold for 20–25 seconds until the yolk is firm but still runny.
Put the egg in the croustade and drizzle with the hollandaise sauce. Serve as canapés.