Called tamago-dofu in Japanese, it has nothing whatsoever to do with soy. Egg "tofu" is a Japanese-style savory steamed custard, which is served chilled with sauce. The Japanese ingredients can usually be found in large supermarkets (in the U.S., at least), or asian specialty markets.
Ingredients:
Custard:
4 eggs
1 cup dashi (Japanese soup stock, instant version is available)
2 tbsp mirin (a Japanese sweetener)
2 tbsp soy sauce
1/4 tsp salt
Sauce:
1/2 cup dashi
1 1/2 tbsp soy sauce
1 1/2 tbsp mirin
2 tbsp bonito flakes
To prepare the custard:
Thoroughly beat the eggs, then stir together with remaining custard ingredients. Pour into a Japanese yokan pan, if you have one, otherwise use a small, square baking pan lined with foil. Cover the pan with foil and place into a preheated steamer. Steam on high heat for 5 minutes, then reduce heat and steam for a further 20-30 minutes, until custard is just set and a toothpick inserted into it comes out clean. Place pan in cold water and cut the custard into 4 pieces. If remove the bottom from the yokan pan, or lift the foil out of your baking pan and tranfer the "tofu" to a plate. Refrigerate.
Sauce:
Combine sauce ingredients and bring to a boil. Cool to room temperature and strain.
To serve:
Place each slice of the custard in its own bowl and spoon the sauce over it. Garnish with a sprig of fresh coriander, if desired.