Two mushroom recipes from an English writer

The Russians are great mushroom gatherers, which you know if you remember the mushroom parties in ''Anna Karenina.'' They have many delicious ways of cooking mushrooms; here are two that are simple and especially good.

The finer you chop the mushrooms, the more the mixture will look like the greenish-gray of Russian caviar - but of course, it won't taste like caviar at all.

English writer Jane Grigson - in her book ''The Mushroom Feast,'' published originally by Knopf (in paper by Penguin Books, $5.95) - suggests you use ceps if you can find them, otherwise cultivated mushrooms. Mushroom Caviar 1 medium onion, minced 2 tablespoons olive oil 1/2 pound mushrooms Salt, freshly ground pepper Juice of 1/2 lemon 2 tablespoons sour cream, or more Chives, chopped

Saute onion gently in oil until almost cooked but not brown. Chop mushrooms, stalks and all, and add to the pan and cook for 8 to 12 minutes.

If mushrooms have a lot of juice, turn heat up; final result should be moist but not too soft.

Season and remove from heat. Add lemon juice, sour cream, and chives to taste.

Serve with toast, well chilled, sprinkled with more chives. Serves 4 by itself, more for hors d'oeuvres.

Grigson also has her own version of mushroom sandwiches, which can be served as a first course, or for a light luncheon. The addition of scrambled eggs and chesse give these added flavor and appeal. Mushroom Sandwiches 1/4 pound of mushrooms, cooked 2 tablespoons butter Lemon juice Salt and pepper 2 scrambled eggs 3 tablespoons Parmesan cheese

Cook chopped mushrooms in butter, then add a little lemon juice; salt and pepper; and cayenne, if you like. Add eggs and cheese gradually to taste.

This makes a good first course to a meal when served with toast. For sandwiches, use a good whole-meal bread.