Step 2

In a medium bowl, whisk the flour, cornstarch, baking powder, baking soda and salt. Add the club soda and whisk until the batter is smooth and the consistency of heavy cream. If the batter gets noticeably thicker as it sits, add an ice cube. Stir the cube around in the bowl—don’t wait for it to melt.

Step 3

Cut firm vegetables, such as carrots, potatoes, celery root and pumpkin, into 1/8-inch-thick slices. Cut softer vegetables, such as mushrooms, zucchini, onions and peppers, into 1/4-inch-thick pieces. Cut fish into 2-inch pieces, and peel and devein shrimp. Cut fruit, such as pineapple and mango, into 1/2-inch- thick slices. Pat all dry before dipping in the batter.

Step 4

Pour enough oil into a medium saucepan to measure about 2 inches. Attach a deep-fry thermometer to the pan; heat the oil to 350°. Line a plate with a double layer of paper towels.

Step 5

Working in batches, drop a few slices of vegetables, fish, shrimp or fruit into the batter; stir gently to coat. Using chopsticks or a fork, lift the food from the batter, allowing the excess batter to drip back into the bowl. Carefully add a few pieces to the hot oil, being sure not to crowd the pan, which will cause the oil temperature to drop, and returning the oil to 350° between batches. Fry, turning occasionally with the chopsticks or fork, until lightly golden on both sides, 1 to 1 1/2 minutes. Using a slotted spoon or strainer, lift the vegetables from the pan, letting the excess oil drip back into the pan. Transfer to paper towels; season with salt. Cover with more paper towels to blot excess oil.

Step 6

In a small bowl, mix the ponzu and Thai sweet chili sauce to serve with the veggie, fish and shrimp tempura.