The recipe is marked easy – but this does not take into account finding Japanese ingredients. I have used easy, ready-made tempura flour. It includes dried eggs and baking powder. I think if you are making tempura on a regular basis you will want to switch to making the tempura from scratch. It’s not particularly hard and all attempts will provide a workable batter, but it is somehow rather stressful. As with most things Japanese, tempura can become an obsessive quest for the perfect crispy and light batter. As they say, practice makes perfect, so you know what to do if you want perfect tempura. The ready-made works well enough (we can trust Japanese food scientists to make convenient products from most culinary processes).
The broth here is made in classic manner by mixing a home-made dashi stock with a stronger home-made flavouring called kaeshi. To make things easier, you can buy dashi ready-made or from packets (dashi no moto – look for the natural versions). You could also dilute tsuyu from a bottle to make a complete soup base.
1. For the dashi, wipe the konbu and soak in the water for at least half an hour. Bring to a boil and just as it starts to boil remove the kelp and discard. Turn off the heat and add the katsuobushi flakes leave to seep for 10 minutes. Strain and set aside.
2. For the kaeshi, add all the ingredients to a pan and slowly bring to a simmer. Turn off the heat and let cool.
3. For the asparagus, snap off the woody base of the stems by bending the spears with your hands. Peel the stalks only if thick and tough. Put the spears into a large and shallow saucepan, cover with boiling water, add a little salt and bring back to the boil. Cook the spears for 1.5 minutes, drain and plunge in cold water, drain again and set aside. For the spring onions slice thinly at an angle. Put in a bowl with a pinch of salt and cover with water, leave for 10 minutes rinse and drain.
4. For the soba, add to a pan of boiling water and simmer for about 4 minutes until just done. Drain reserving a little of the water in the pan. Return to the pan and add a few drizzles of sesame oil, stir and set aside.
5. Bring the oil to temperature (180C).
6. Prepare your work station. You will need: a dish with kitchen towels to drain the finished tempura; tongs/slotted spoons for the oil; a plate on which to make the fritters with a silicon spatula (or large spoon) to transfer the fritter; a small bowl to mix the asparagus; a larger bowl to make the batter using a fork; a spoon to transfer the batter.
7. Cut the asparagus on a very acute angle along the spears, each about 6 cm long in total. Put into piles of about 3 or 4 spears each – a small handful. Season the piles with salt and pepper. Make the batter by adding the water to the flour and stirring with a fork, do not over work/whisk or beat. Work in batches. Take a pile of asparagus and put into the small bowl. Add about 1 tablespoon of tempura batter mix and coat well with your hands, lift up the asparagus and shake off excess flour. Transfer to the plate and add a couple spoonfuls of batter and mix with your hands to make a flat clumpy fritter. Carefully, take the plate to the oil and lower to the surface, then slowly but steadily, using a spatula or spoon, slide the fritter into the oil without dropping or splashing. Keep the oil at temperature and fry on one side for about 3 minutes and then on the other for about another 1 – 2 minutes until done and crispy. Remove from the oil and drain. Continue with the other batches of asparagus.
8. Make the broth by putting the dashi in a pan and heating. Add 100ml kaeshi and heat, then taste – adjust adding more kaeshi to taste. The broth should be full of flavour but broth-like, so not too strong – you can always add more soy at the table. NB: any leftover kaeshi will keep in the refridgerator for a few months (make a dipping sauce – mentsuyu – by increasing the ratio of kaeshi to dashi to taste).
9. Divide the soba between bowls, add the hot broth and garnish with chopped spring onion and shimi togarashi to taste. Serve with the tempura fritters.