To Make the Tentsuyu Dipping Sauce
- Add kombu into a saucepan with ¾ cup water. Bring to a boil, remove from heat and add in the bonito flakes. Allow to steep for 10 mins, and then strain through a sieve.
- Return this dashi stock back into the saucepan and add remaining sauce ingredients. Bring to a boil, and then remove from heat and set aside to cool.
To Cook the Tempura Vegetables
- Heat oil in a saucepan or pot to 170°C.
- Add panko breadcrumbs into a bowl.
- In a separate mixing bowl, add flour and egg white. Slowly pour over soda water while whisking slowly until just combined with some lumps in the batter.
- Dip eggplant and sweet potato slices into tempura batter and then coat in panko breadcrumbs.
- Carefully drop into hot oil and fry until crispy and golden brown. Fry in batches until remaining ingredients are finished. Carefully remove and drain on paper towel.
- Serve with Tentsuyu dipping sauce.