Cookery lore of Australia

Chances are you've never been served barramundi cooked by an aboriginal fisherman, with the whole fish wrapped in fleshy leaves and buried in the ashes of the campfire to cook slowly in its own juices.

But when Colleen McCullough describes it in her book about Australian cooking , it sounds unusual and fascinating, even though you know you'll probably never get to Australia to sample the food.

''For most of us,'' Ms. McCullough writes, ''the only barrramundi we will ever handle are the steaks or cutlets from the fish shops.'' The author of ''Thorn Birds'' collaborated with Jean Easthope, a longtime friend, in ''Cooking with Colleen McCullough & Jean Easthope'' (Harper & Row, $14.95).

In a sense there is no Australian cuisine as such, the authors say, for what Australians eat has many of its roots in English food that was transported across the seas and adapted to the country's native and available ingredients.

The dishes changed radically over the years to suit the environment and needs of this island continent.

The country's famous meat pies, Pavlova, the beautiful meringue dessert; potato and hot and cold puddings are among the wide range of recipes.

Although Australians have a long coast they don't eat as much fish as you would expect, the authors say.

''If a fish looked a bit familiar, our British ancestors gave it a familiar name, which causes much confusion today,'' the book explains.

''The Australian sea salmon, for example, is a member of the perch family, and no relation to its northern namesake. They are frequently thrown back because of the dark color of the flesh - a terrible waste because it is delicious when properly cooked.''

Turn-of-the-century drawings, photographs, and charming paintings and sketches illustrate Australia through the present day and bring the land and people, as well as the cuisine, alive to the reader.

Here is one of the sheepshearer's cook specialties, and a great favorite during colonial days. It is not like the American brownie since it has no chocolate.

The authors give credit to Mrs. J.M. Hodgson of Eulabar, Merriwa, N.S. W. for the recipe. Australian Brownie 2 cups sugar 2 cups sultanas (raisins) 1 cup water 225g (1/2 lb.) butter 4 cups plain flour 1 teaspoon bicarbonate of soda 2 teaspoons baking powder 1 teaspoon allspice 1 teaspoon each nutmeg, cinnamon and ginger

Combine first 4 ingredients in saucepan, bring to boil and boil gently 3 minutes, stirring. Cool.

Sift remaining ingredients together and gradually stir them into the cooled mixture, mixing well.

Use the dish you use for roasting a leg of lamb or piece of beef and line with 2 layers of greased brown paper. Pour in batter and smooth evenly.

Bake at 170 degrees C. or 350 degrees F. 60 minutes then turn out on wire rack to cool. Leave paper on until cool, then peel off.

Serve sliced and buttered.

If you prefer you can bake in papered loaf tins instead of the roasting pan and bake at same temperature 55 minutes,or until a skewer comes out clean.

However, the shearer's cook never carried such things as cake or loaf tins, and did all his baking in the same tins,no matter whether it was a roast of meat ,a brownie or scones.