In a small mixing bowl, soak dried shiitakes in 1/2 cup warm water until softened, about 5 minutes. After softened, remove from the bowl reserving the liquid, and chop into pea-size pieces. Set reserved liquid aside.
Make 1 cup of dashi and set aside.
In a medium size mixing bowl, add eggs, soy sauce, salt (optional) and beat until fully combined.
Add dashi stock and mushroom water into the egg mixture and stir to combine. To ensure a silky smooth chawanmushi, you can optional stain the entire mixture.
Pour mixture into heat-safe bowls and add cut mushrooms.
Fill a large stovetop pot with enough water to cover 1/2 inch off the bottom. Place bowls into the pot and bring water to boil. Once boiling, reduce heat to low, cover 7/8 and cook for approx 10-12 minutes. If the steamed eggs don’t look fully set, continue to steam for another 2-3 minutes.
Once fully cooked, use mittens to carefully remove ramekins or bowls from the pot and serve. Note – bowls will be extremely hot so proceed with caution.