Northern Thai sour curry soup

There are all kinds of soups in Thailand, made with all kinds of seafood, poultry and meat. The one thing they all have in common is that intriguing flavor that is simultaneously sour, salty and spicy. Thais call this flavor yum.

Yum is the most important flavor in Thai cookery. You may recognize the word “yum” in Thai dishes like yum nuea (spicy beef salad) and tom yum soup.

When friends are sitting around thinking of Thai food and its bold flavors, they are thinking of yum. Yum is a taste bud nirvana.

The ingredients that give us this magical combination are the basics of the Thai kitchen. Salt is rarely used; instead there is fish sauce (nam pla), a liquid made from salted fermented fish. It doesn’t sound very appetizing, but it is indispensable in Thai cooking. Many other countries have variations of fish sauce, and each is a little different. It is always recommended that cooks use the fish sauce from the particular culture whose food they are cooking.

Sour flavors are derived from limes and sour tamarind. Limes are always used to flavor soups because their sourness has a slightly sweet finish. They also do not color food when added. Lemons and tamarind tend to be slightly more bitter in the finish and are more often used in stir-fry.

Spiciness comes from small, skinny Thai chiles. When fresh, they range from half an inch to an inch and a half long. Before the chiles are added to soup, they should be smashed to release their flavor. Remember, fresh chiles are hotter than dried and red chiles are hotter than green.

Thai chicken stock is made with chicken bones and three essential Thai flavorings: lemon grass, galangal and makrut lime leaves.

Lemon grass is a long, reedlike herb that measures about 1 to 2 feet high with a bulbous base similar to a green onion’s. Only the lower half of a lemon grass stalk is used, because only it contains an oil called citral, an aromatic compound also found in lemon peel. Citral is what gives lemon grass its citrus-like flavor.

To use it in soup, remove the upper half of the lemon grass stalk and discard. Cut the bottom half into 2-inch sections on the bias. Give them a good smash with the side of your knife before adding them to the stock. Lemon grass is edible, but it is tough unless cooked and tenderized.

Makrut lime leaves come from the makrut lime tree, indigenous to Southeast Asia and Hawaii. They have a double-leaf shape and give off a mysterious aroma with citrus and floral qualities. The leaves are used whole to flavor soups and they can be cut into very thin strips and stir-fried.

Like lemon grass, makrut lime leaves are tough but edible. They need to be cut into small enough pieces that can be cooked and tenderized quickly. The peel of the makrut lime fruit is also used in making curry paste.

Galangal is often mistaken for ginger, but galangal root has a unique flavor: spicy with an elusive floral quality. It can be purchased dry or fresh, the fresh having a much stronger flavor. Fresh galangal is available in frozen vacuum-packed form.

You don’t have to go out to eat great Thai. Thai soups are a comfort food. Why not enjoy them in the comfort of your home?