Q. Please discuss the different kinds of potatoes available in the supermarket and what dishes to use them in. I'm tired of mashed potato stews and limp french fries.

A. From a produce handler's perspective, there are four kinds of potatoes:

The russet -- Has a dry, mealy texture, a leathery skin and shallow eyes. The russet is grown in many states, the most important being Idaho, New York and Maine. It represents more than half the nation's annual crop.

*The long white potato -- Has a firm texture and thin, smooth skin, a light-tan color and shallow eyes.

*The round red potato -- Has a firm texture, a smooth, reddish skin and deep eyes.

*The round white potato -- Has a firm texture and creamy color. Most varieties of potatoes belong to this category.

While these descriptions mean something to the produce handler, they are meaningless to a cook. There are actually more than 30 important commercial varieties of potatoes, each of which falls into one of the above categories.

When purchasing potatoes, one should consider three factors:

*Mealiness -- A mealy potato (namely, the russet) makes fluffy, grainy mashed potatoes, crisp but grainy french fries and a fluffy baked potato and is adequate for any purpose except scalloped, boiled or steamed potatoes or stews. In these dishes, its mealy texture, caused by large starch granules that don't adhere to each other, causes the potato to disintegrate.

*Moistness -- The more moist the potato, the gummier the french fry, baked or mashed potato. There are varieties that are not mealy but produce crisp french fries with creamy interiors and fluffy, smooth mashed potatoes, but they're hard to find and to detect because potatoes are not sold by varietal name but by category. Fast-food restaurants sometimes produce the best french fries because they are able to contract with farmers who grow varieties according to their specifications. Moist-fleshed potatoes are excellent scalloped, boiled, steamed or in stews. The "new potato," any variety picked immature, has a high water content. New potatoes look prettier because their skins are thinner.

*Size -- One should also select a potato size and shape according to purpose. The long white is often used for french fries because of its length. The round red is often preferred for boiled potatoes; one need only cut the potato in half and remove skin and blemishes with a few strokes of the paring knife. The russet makes the most attractive baked potato because of its size and shape. And the round white (which cooks call a "chef potato") is just your all-purpose spud.

Q. Why can't one broil meat in a toaster oven? There's a warning against it engraved into the toaster oven tray. This appliance seems perfectly suited to the task.

A. The openings of most toaster ovens are only 3 or 4 inches high. When you turn on a toaster oven, two elements -- one overhead, the other underneath -- begin to glow. Unlike ovens and broilers, toaster ovens are small enclosures that trap fat droplets; conditions are just right for a modest inferno.

Steaks and hamburgers are 60 to 75 percent water and 10 to 30 percent fat. If you broiled them directly on the wire rack, the fat would drip underneath onto the bottom coil and immediately start a fire. You would find it difficult to extinguish.

If you used the tray, a fire also would start -- just a little later. While the fat no longer would drip onto the bottom coils, it still would collect on the tray. As the meat cooked, its water would ooze into the hot fat, which would have spread in a thin layer across the tray. The tray and fat being very hot, that water instantly would flash into steam and atomize much of the fat, the tiny droplets of which would catch fire when they reached the upper element.