Prepare the dashi broth and keep it warm.

In a large mixing bowl, whisk the eggs until fully combined and smooth.

Slowly pour 400 mL of dashi broth into the eggs while whisking continuously to prevent the eggs from curdling. Stir in the mirin and salt.

Strain the egg mixture through a fine mesh sieve into another bowl to remove bubbles and ensure a silky custard texture.

Place tofu pieces at the bottom of ramekins or small heatproof cups.

Gently pour the strained egg mixture into the cups over the tofu.

Place the cups in a water bath setup inside a pot or steamer. Cover the cups with plastic wrap, foil, or lids to prevent condensation from dripping onto the custard.

Fill the pot with water so it reaches about halfway up the sides of the cups. Bring the water to a boil, then reduce the heat to a gentle simmer.

Steam the chawanmushi for 15 minutes, or until the custard is just set and silky.

While the custard cooks, prepare the sweet potato puree. Steam the sweet potatoes until very soft, then blend them with 150–200 mL of the remaining dashi broth until smooth and creamy.

Once the chawanmushi is finished, spoon the sweet potato puree over the top.

Garnish as desired and serve warm.