Preserving shiso, basil, lemon verbena, and other herbs
Around here it's already cool enough to declare that summer is over and fall is here. (Actually we had a very cold, wet summer anyway, but nevertheless.) So the summer vegetable plants in my garden are dying off, and I'm in the process of salvaging the tomatoes and eggplants, picking the last zucchini, and eyeing the winter squash to see when they will be ready.
Tender herbs like basil are on their last legs, so I'm picking and preserving those flavors of summer so that they can brighten the dark winter months. Last year I took the lazy option and froze everything, packing the picked leaves in plastic bags and throwing them in our big locker-type freezer. Freezing is okay if you're too busy to do anything else with your herbs, but not really the optimal way all the time to keep tender herbs in the long run. So this year I'm thinking things through a bit more and considering how I want to use each herb, and preserving them accordingly. Each method is quite easy and really doesn't take that much time.
In the summer I like to throw basil leaves into everything from soups to sauces to salads. For that though you do need fresh leaves. Frozen leaves darken and don't really look nice in a salad. (You can keep a basil plant or two going under growlights in pots for garnishing if you're determined to have it fresh year round.)
I rarely if ever have basil in anything but savory dishes, so a savory preserving method was the logical choice. After trying various methods I have settled on making a basil puree. This is essentially a pesto without the cheese, garlic and pine nuts.
For every 2 cups of fresh basil leaves (lightly packed into the measuring cup), use 1/2 cup of light olive oil (I prefer a light, relatively flavorless olive oil so that the basil flavor really shines through, but you can use an extra virgin if you prefer.) Be sure to pick the leaves only from the stems. Wash the leaves then pat them dry with kitchen towels.
If you are a purist you will mash the leaves with a mortar and pestle, but I use the food processor. Whiz up the leaves until chopped, and add the oil to make a puree. Add a few drops of lemon juice, and a little salt (1/4 tsp. or so per 2 cups of basil).
I freeze this spread thinly in plastic zip bags. To use, just break or cut off as much as you need. You can turn this into pesto by adding freshly grated Parmesan, crushed or grated garlic, and ground pine nuts. (The easy way of course is to whiz everything together in the food processor.)
For what it's worth, I had about 16 cups of basil leaves, which turned into about 4 cups of basil puree. The puree keeps the bright flavor of basil very well.
(Basil thoughts: This year I grew a variety of basils, but next year I am going to grow mostly the classic Genovese basil or 'sweet' basil, and perhaps just one plant each of the small leaved basil, Thai basil, and lemon basil. The Genovese basil really is the most useful, and also makes the nicest pesto or puree.)
I use lemon verbena mostly in drinks and desserts, so it makes sense to preserve (or conserve...I'm never sure which term is correct for what method) it with sugar. This recipe is from a wonderful book called The Herbfarm Cookbook, but I've adjusted it just a bit by reducing the sugar.
For every 2 cups of fresh lemon verbena leaves (lightly packed in the measuring cup), use 1/2 cup to 3/4 cup (or 1 cup as is suggested in the book) sugar. I use natural brown cane sugar, but white sugar is fine of course. Puree in the food processor until it forms a paste. Freeze in the same way as the basil puree. This stuff is wonderful sprinkled onto fruit - especially if you broil the fruit, or used as flavoring in all kinds of dishes. You can also stir in a couple of spoonfuls into boiling water for an instant lemon verbena tea. (Strain out the bits with a tea strainer.)
You can also try drying lemon verbena, but to me drying takes away much of the soul of this wonderful herb.
This method also works pretty well with mint leaves. Jamie Oliver had a recipe for pineapple slices sprinkled with mint sugar in one of his books. It should also work with lemon balm, though I haven't tried it.
Shiso, which I consider to be one of the most essential Japanese herbs, is used mainly in savory dishes. Red shiso leaves are used to make umeboshi (they color the plums and give them a distinct flavor). I don't make umeboshi since I don't have access to the plums, but shiso on its own can be enjoyed preserved. This year, I just had one red shiso plant and several green shiso plants, which I used almost every day - as garnish, tempura, in salads and more. (Shiso is a nutrition powerhouse with loads of vitamins, calcium, fiber and so on.)
The traditional way to keep either red or green shiso leaves is to preserve them in salt.
Salted shiso leaves
First, select large, unblemished leaves only. (The alternate name for green shiso leaves is ohba, which literally means 'large leaves'.) Just wash and dry the leaves carefully, and pack down in a non-reactive container (glass, ceramic, plastic or enamel - not anything metal) sprinkled with salt between each leaf. Leave, well covered, in the refrigerator for at least a few days. The leaves will exude moisture and become a rather dark green (or darker red if you're using the red leaves).
Don't mix red and green leaves by the way - the red leaves will discolor the green leaves, turning them into an unattractive muddy brown. Besides, the red leaves have more bitterness and need to be rested a bit more after salting.
The salted leaves can be rinsed off a bit or used as-is. Salted shiso leaves are great onigiri wrappers - use instead of nori, and don't salt your hands or mold when forming the balls. You can also wrap the leaves around ground pork, chicken or beef patties, or even veggie patties, and pan-fry them to make a crispy, fragrant surface. You can do this with fresh shiso leaves too (actually it's better with fresh leaves). The leaves can also be shredded and tossed with hot pasta. Since the leaves are salty, adjust the amount of salt overall in the dish.
If you have some shiso seed heads (hojiso) they can also be salted in this manner.
Yukari is a furikake-type powder made from dried salted red shiso leaves.
Another way to preserve shiso is to marinate them in soy sauce with some garlic cloves. I first saw this method on the wonderful Japanese cooking community site Cookpad.
Shiso leaves in garlic soy sauce
Simply cut up some garlic cloves, and place with several shiso leaves in soy sauce. Leave for at least a day; store in the refrigerator.
The leaves don't last that long in the soy sauce (about a month), though you can make them last a bit longer by quickly blanching the leaves in boiling water beforehand. The soy sauce becomes pleasantly flavored with the shiso and garlic, which makes it great to use in cooking, salad dressings and so on.
Finally, I do pack some of the small leaves in plastic bags and store them in the freezer, to use as garnish for noodles, soups and such. Still, shiso is one of the flavors of summer for me, so I can't wait to sow some seeds next spring for fresh, green leaves in the warm months.
You can also try sprouting shiso seeds indoors and clipping the seedlings (called mejiso) - this is a rather trendy garnish at the moment. Shiso seeds do take some time to germinate though.
Other herbs: drying, freezing and flavored oils
Parsley, coriander and chives are pretty cheap to buy and much better fresh, so I don't really bother to preserve them. If you want to though, I think the best way is to chop them all up and store pressed out thinly in plastic bags, which go in the freezer. They stay reasonably green and fragrant this way. Just break off what you need. You can also try freezing them with a little water in ice cube trays, but I find this to be too fiddly - and I never have enough ice cube trays.
Small, tough-leaved herbs such as rosemary, thyme and oregano do a lot better in their dried form than tender-leaved herbs do. I dry some sprigs by putting them in a paper bag with handles and hanging the bag on a door handle. The bag allows air circulation and catches any dropping leaves. When the leaves are completely dry, strip them off the stems and store in airtight containers. But if you live in a mild climate, these tough herbs may survive the winter for you. (Here rosemary does stay sort of green, but the other herbs die down to the ground.) If you have enough light, a pots of these tough perennial herbs may survive the winter on a sunny windowsill or under grow lights.
I've often seen decorative dried little bundles of thyme and bay leaves in Provence, tied up with string. If you have the patience this may be worthwhile.
You can make flavored oils with these herbs too, though they seem to fare better when you add garlic to the mix. Just fill a bottle or jar with olive oil, and pack it as full as you can with the herb of your choice plus a few cloves of garlic. Leave for at least a week, preferably longer. Strain, then optionally re-package with a decorative sprig of the same herb in the oil. This makes a very decorative present.