Prepare the solid fillings: thinly slice the Shiitake Mushroom, parboil or roast the Ginkgo Nuts if they are raw, and cut the Kamaboko into thin wedges.
Trim and cut the Chicken Thigh into small bite-sized pieces, season with a pinch of Salt and a splash of Sake, then briefly sear or poach just until cooked through. Peel, devein and give the Shrimp a quick blanch or sear with a little Sake so they are just opaque.
Make the custard base: gently beat the Eggs in a bowl—avoid overbeating to reduce bubbles—then slowly stir in warm (not boiling) Dashi until smooth. Season the mixture with a little Light Soy Sauce, Mirin and, if needed, another tiny pinch of Salt.
Strain the egg–dashi mixture through a fine sieve into a measuring cup or jug to remove any foam and ensure a silky texture.
Divide the prepared fillings between small ramekins or chawan cups, arranging chicken, shrimp, shiitake, kamaboko and ginkgo neatly. Pour the strained custard over the fillings, filling each cup about three-quarters full. Wipe the rims and cover each cup with foil or a lid to prevent water dripping onto the surface.
Steam gently: bring a pot of water to a low simmer, place the cups in a steamer or on a rack, cover, and steam over low heat for about 12–18 minutes (smaller cups ~12 min, larger up to 18–20 min) until the custard is set but still slightly wobbly in the center. Avoid a rolling boil to keep the custard smooth.
Turn off the heat and let the cups sit covered for 2 minutes before uncovering. Garnish each chawanmushi with a small sprig of Mitsuba and a little Yuzu Zest for fragrance. Serve warm.
