Add the flour, cornstarch, baking powder, and salt to a large bowl and stir until well combined.
Add the sparkling water gently, while you’re whisking until well combined, but don’t over-mix. You can use a whisk, a fork or your chopsticks. Set aside.
Dip veggies into the batter, one at a time, to lightly coat, shaking off any excess batter.
Pour the oil into a saucepan, wok, pot or a deep skillet and when it’s hot, add the veggies. Cook for 1-2 minutes. Flip and cook 1-2 minutes on opposite sides. You could also use a fryer, but I prefer this method.
To make your tempura extra crispy and extra beautiful, dip your chopsticks into the batter and just pat on the veggies. Repeat a few times on each piece of tempura. This step is optional.
Don’t add too many veggies at the same time or the temperature of the oil will drop and your tempura will go soggy. I usually add 4, but the number may vary depending on the size of your veggies. If you want to save time and you don’t mind about getting a better result, just add as many veggies as you want.
Transfer the veggies to a cooling rack, that way they won’t go soggy and also they will be less greasy. You can also use a paper towel, but the rack works amazing and is also zero waste.
To make the sauce, just mix all the ingredients in a saucepan, bring to a boil and simmer for 5 minutes.
Serve the vegetable tempura and the sauce immediately. You can keep the sauce in an airtight container or a jar in the fridge for at least 1 week. The tempura is best when fresh, but you can keep the leftovers in an airtight container in the fridge for 3-4 days. The sauce is optional, but your tempura pieces will taste much better if you dip them into the sauce.
Feel free to use any flour you want or have on hand.
You can also use any starch, or even omit this ingredient, but I think the batter works great with some kind of starch in it.
Any oil will do. Extra virgin olive oil is my go-to. The amount of oil may vary depending on the size of the saucepan, wok, pot or skillet you’re using.
Pretty much any veggie is okay to make tempura.
Mirin is a Japanese sweet wine. You could use some white wine instead, but I would add only 1 or 2 tablespoons and more vegetable stock. You can also use only vegetable stock instead.