Does your customer also need herbs from the Gobi Dessert? Seasonings from the Arctic Circle? A pinch of lunar dust, perhaps? She will have about as much success turning up cassia buds. Frankly, what she needs is a less fussy recipe - which, from the goodness of our hearts, we will provide. But first, a bit of background.

The cassia tree (cinnamomum cassia), which is native to Myanmar (Burma), is a very close relative of the cinnamon tree (cinnamomum zeylanicum), which is native to Sri Lanka (Ceylon). Both trees are the sources of cinnamon sold in much of the world, although in some countries a distinction is still made between cassia and cinnamon. Alert cooks can tell them apart. Ground cassia is a darker red-brown, and has a coarser, more pungent, almost bitter taste. Ground cinnamon is lighter ("buff colored"), and has a sweeter and gentler taste. The cassia and cinnamon sticks come from the inside of the bark after the trees have been cut down during the rainy season, when it is more pliable. But, unlike cinnamon bark, which curls itself into neat quills or scrolls when it dries, the cassia bark curls in a less uniform, less compact pattern. Cassia is the less expensive of the two.

Cassia buds are the dried, unripe fruits of the cassia tree and resemble cloves, although they are smaller and darker. They have been used in cooking for some 5,000 years, and impart a "warm, mellow cinnamon flavor which is excellent with fruits," according to Alice Arndt, author of the wonderful Seasoning Savvy (Canada, UK).

Unfortunately, however, cassia buds are only commercially produced in the jungles of China and Vietnam. And there is apparently not enough demand, at least in this part of the world, to justify harvesting and exporting them. The Spice House in Evanston, Ill., (847-328-3711) occasionally receives shipments of cassia buds, but says the best substitution is 3/4 teaspoon of cassia bark for every teaspoon of cassia buds called for in a recipe.

Your customer is right - a cinnamon flavor is an integral part of most pickled watermelon rind recipes, but it can come in the form of cinnamon or cassia sticks or cinnamon or cassia oil with much less effort than it takes to track down cassia buds.

Watermelon Rind Preserves From The Glass Pantry (Canada, UK), by Georgeanne Brennan.

Every year of my childhood my grandmother made these thick preserves, and every year I disdained them. Later, as an adult, I discovered they were a perfect condiment for East Indian curries, along with yogurt and chopped fresh cilantro and tarragon leaves. The texture of these preserves is firm and the taste is of clove and cinnamon. The most suitable melon, if you can get it, is the old-fashioned citron melon, with its solid three- to four-inch-thick rind. Since these melons are hard to come by, a good substitute is an underripe watermelon with a thick rind.

Ingredients:

1 pound watermelon rind 5 quarts water 1/2 cup salt 2 cups granulated sugar 1 lemon, sliced 1 cinnamon stick, about 2 inches long 1 teaspoon whole cloves

Instructions:

Peel the skin from the rind and scrape the rind clean of any flesh. Cut the rind into 1/2-inch cubes. Combine 4 quarts of the water and the salt in a large bowl and stir to dissolve the salt. Add the rind and let soak overnight at room temperature.

The next day, drain the rind. Place it in a stainless-steel or other nonreactive saucepan with 2 cups of the remaining water and bring to a boil over high heat. Lower the heat and simmer until the rind is just tender when pierced with a fork, about 50 minutes. Drain well and set aside.

In a saucepan large enough to hold the rind eventually, combine all the remaining ingredients, including the remaining 2 cups water. Bring slowly to a boil, stirring to dissolve the sugar. Boil until the sugar dissolves and a syrup forms, about 5 minutes. Add the rind and cook over low beat until it becomes transparent, about 30 minutes.

Using a slotted utensil, remove the rind pieces and pack them tightly into hot, clean, dry jars with sealable lids. Ladle the hot syrup into the jars, filling the jars to within 1/2 inch of the rims. Using a damp cloth, wipe the rims clean. Cover with the lids and process for 30 minutes in a hot-water bath.

Remove the jars and let them cool 12 hours or overnight. Check for a complete seal.

Store the sealed jars in a cool, dark place. The preserves will keep for up to 1 year. Once opened, keep refrigerated. Store any jar lacking a good seal in the refrigerator for up to 2 weeks.

Yield: Makes 2 to 3 pints.

Related Article: Another Recipe for Watermelon Pickles