Chawanmushi (Japanese Savory Steamed Egg Custard)

Crack and weigh 3 large eggs (50 g w/o shell) in a measuring cup or bowl set over a kitchen scale. Multiply the egg weight by 2.5 to calculate how much dashi to use and add it to the eggs.
Nami's Tip: For example, 150 g eggs x 2.5 = 375 ml dashi (egg-to-dashi ratio of 1:2.5). To measure the dashi, I zero out (tare) the scale and pour the stock directly into the eggs. I weigh and mix everything in a glass measuring cup for easy pouring later.
Add 1 tsp mirin, 1 tsp soy sauce, and ½ tsp Diamond Crystal kosher salt to the egg mixture.
Nami's Tip: Add less or more seasoning for how much egg you used, as I based these measurements on an egg weight of 150 g. If you have it, use usukuchi soy sauce because it keeps the custard color lighter.
Whisk the egg and dashi mixture until the egg whites and yolks are fully combined.
Strain the egg mixture through a fine-mesh sieve into another bowl.
Nami's Tip: Straining achieves a refined silky texture.

Cut 2 chicken tenders into ½-inch (1.3 cm) pieces. Place in a tray or bowl, toss with 1 Tbsp sake, and marinate for 10 minutes.
Cut 8 slices kamaboko (fish cake) thinly. Trim the roots off 1.8 oz shimeji (brown beech) mushrooms and separate them into small clusters.
Loosely knot each stem of the 4 sprigs mitsuba (Japanese parsley). Alternatively, thinly slice the green onion if using instead.

Place the chawanmushi cups (with lids or foil covers) in a large pot. Add enough water to reach halfway up the sides, then remove the cups. Cover the pot, bring to a boil, and turn off the heat.

Layer the chicken on the bottom of each cup, then add the shimeji mushrooms and ginkgo nuts (if using).
Arrange kamaboko and mitsuba (or green onion) on top. Pour the egg mixture until cups are 80% full, keeping the top layer partly uncovered. Remove any air bubbles with a spoon or skewer.
Nami's Tip: Air bubbles create a rough texture on the cooked custard.

Bring the pot of water back to a boil and reduce to the lowest heat. Keep the water between 176–194ºF (80–90ºC) throughout steaming. Carefully lower the cups into the water, cover with their lids, and set the pot lid slightly ajar. Steam for 20 minutes, or 15 minutes if you omitted the chicken.
Nami's Tip: Monitor closely, as the size and thickness of your cups affects the cook time. Do not boil, or the finished custard will not be smooth.
Test doneness by inserting a skewer into the center: clear liquid means it's ready. Tilt to confirm the custard is set throughout, then carefully lift the cups from the water.
Nami's Tip: I removed the lids first and lifted out the cups with a hot plate gripper.

Refrigerate leftovers in their cups for up to 2 days. To reheat, steam for 2 minutes until warmed through.