The classic tempura batter works for all vegetables, but I love it especially with shiso leaves, eggplant, Spanish onions, peppers, sweet peas and sweet potato.
Besides the classic tempura batter, I make a fragrant batter using buckwheat flour. It's a tempura variation called kimpura. The name is derived from the earthy gold color of buckwheat. It is a gluten-free vegan batter that isn't as fluffy as the classic tempura batter but is light and nutty in flavor. (This would have been the perfect batter to serve the high priest).
The texture of the batter is smooth and slightly runny. It can be used like the classic tempura batter, and I think it works especially well for kabocha squash, carrots, haricots verts and zucchini blossoms.
Another way of deep-frying vegetables is a batter-less method called su-age. It works best with waxy skinned vegetables such as pumpkin, carrots, burdock and eggplant — vegetables that can hold their shape in hot oil and produce a crispy skin.
I like the way su-age intensifies the flavors of the vegetables and brings out their natural sweetness. You can cut the vegetables thin and make crispy chips, or cut them thick and make a batter-less tempura. I serve su-age vegetables as an appetizer and they disappear as quickly as I serve them.
Whenever you are making tempura, make sure you set the table before you begin frying. Have the plates, dipping sauce, seasonings and chopsticks ready to go. Serve the tempura close to the kitchen so everyone can eat it right away, piping hot. Don't wait for everyone to sit down at the table. And whatever you do, don't put the finished tempura in the hot oven and wait for the others to fry. That defeats the purpose.
And if you have a guest asking for shrimp when all you are serving is vegetable tempura, give him the baby carrot fried whole with its young leaves intact. If he is a nice person, he will bite into the crispy leaves and appreciate your efforts.