Prep all the veggies to the desired size.
Heat a Dutch oven filled with 2-3″ oil to 350°.
Combine 1 cup of flour and the cornstarch in a bowl and set aside.
In a separate bowl, combine 1 cup flour, baking soda, salt, and the eggs. Whisk to combine. Add in the water and whisk until smooth. The batter will be watery.
Dredge the vegetables in the dry mix, then the wet and place in the fryer. Fry several pieces at a time until browned. If you prefer, you can double dredge the vegetables before frying.
Remove from oil and drain.
Serve with a traditional dipping sauce by combining 3/4 cup miso broth, 2 tablespoons soy sauce, and 2 tablespoons mirin. Top with scallions.