MICROWAVE COOKING

THERE is more to fish than simple grilling. There are many great soups that are hallmarks of the regions where they were developed. And in any season, a fish soup can introduce a meal or become a whole one.

Many soups are better when started with a strong fish broth. The microwave oven can make terrific broth quickly and with less kitchen odor than traditional methods. And microwave cooking elicits more flavor from the fish without destroying its texture.

In Portuguese fish stew, the richness of mackerel obviates a need for broth and contrasts pleasantly with the hearty taste of kale. This dish seems to be a fish variation of that Portuguese classic, caldo verde, a meat dish described in Jean Anderson's ''Food of Portugal,'' (William Morrow, 1986).

An ample party dish like Alberto Ciarla's fish soup is best made in quantity. It does not cook well in a low-wattage oven. Mr. Ciarla is the chef and owner of an extraordinary fish restaurant in Rome that carries his name. The soup served there is much richer and more elegant, but the version here is good.

Of these recipes, only the creamy oyster soup is a traditional first course and can be made in a low-wattage oven. With its subtle taste and saffron color, it is a good start for a very festive dinner. Portuguese Fish Stew Preparation time: 30 to 40 minutes Cooking time: 46 minutes 1/4 cup olive oil 2 pounds potatoes, peeled and sliced 1/4-inch thick, about 5 cups 2 1/2 pounds mackerel, filleted, with heads and bones cut into 2-inch pieces 3 1/2 cups dry white wine 20 cloves garlic, smashed and peeled 1 1/4 pounds kale, stemmed, washed and cut into 1-inch slices 1 1/2 tablespoons kosher salt Freshly ground black pepper, to taste.

1.Stir together oil and potatoes in a 5-quart glass or ceramic casserole. Cover securely with microwave plastic wrap or a tightly fitting lid. Cook at 100 percent power for 4 minutes in a 650- to 700-watt oven. If using plastic, prick to release steam.