Japanese egg salad sandwich (Tamago sando)

1. Put the eggs into boiling water, cook for 10 minutes, then cool in iced water and peel.

2. Mash the eggs finely with a fork – the yolks should be very fine, the whites can stay a bit chunkier.

3. Stir in the mayonnaise and the pinch each of sugar, salt and pepper until creamy.

4. Spread one side of each bread slice thinly with the butter mixed with mustard, so the bread doesn't go soggy.

5. Spread the egg mixture thickly on two slices, cover with the other two and press gently; wrap in cling film and chill for 10 minutes.

6. Trim off the crusts with a sharp knife and serve the sandwiches halved or cut into triangles.

Tip: Tamago sando is the cult sandwich of Japanese convenience stores (konbini): soft, crustless bread and creamy egg. It's most authentic with Japanese mayonnaise (Kewpie) and soft milk bread (shokupan).