"Thanksgiving is my favorite holiday," says Dianne Orkin Footlick. "I just love everything about it, not only the informality of the whole day, but because everyone else brings food, and I provide the ice cubes."

Well, that is a bit of an exaggeration, because sometimes Footlick contributes a casserole called Mushrooms Florentine, a recipe she got from her mother in Jackson, Miss.

Footlick is not known for her love of the kitchen. She does love good food, however, and she has mastered a very small but select collection of recipes.

"I owe my appreciation of good food to mama," she says. "Every time I go home to Jackson I get some new recipes pressed on me. They say 'Here Dianne, here's one even you might use.' They know I won't read a recipe if it has more than four ingredients in it."

If you are looking for a new side dish for your Thanksgiving menu, Dianne's recipe for Mushrooms Florentine is one that can be made ahead. DIANNE FOOTLICK'S MUSHROOMS FLORENTINE (8 servings) 2 packages frozen chopped spinach 1/2 pound small mushrooms 5 tablespoons butter 1 medium onion, chopped 1/3 pound grated cheddar cheese 1/2 teaspoon salt 1/8 teaspoon pepper Garlic salt

Defrost spinach and drain thoroughly. Saute the onion in 4 tablespoons of the butter until limp and translucent. Remove stems from mushrooms. Reserve 10 or 12 mushroom caps for the top of the casserole. Chop remaining caps and stems and saute them with the onion. Mix the onion/mushroom mixture with drained spinach and salt and pepper. Saute reserved mushroom caps in remaining 1 tablespoon butter.Spread the spinach mixture in a baking dish; top with mushroom caps; distribute cheese over all. Sprinkle with garlic salt. Bake at 350 degrees for 30 minutes.

You may want to substitute the following casserole in your menu to give one of your old faithfuls a rest. It was created by Mrs. Carlson, a caterer who practiced her trade in Sioux City, Iowa: SCALLOPED CORN AND OYSTERS (8 servings) 1/2 cup butter 2 cups crushed soda crackers 1 can cream-style corn (about 2 cups) 1/2 cup half-and-half 1/2 teaspoon salt 1/4 teaspoon pepper 1 pint oysters 2 shakes hot pepper sauce

Melt butter in a large saucepan. Crush soda crackers coarsely and stir into butter. Mix together the corn, half-and-half, salt, pepper and hot pepper sauce. In a baking dish, make 2 layers in this order: cracker/butter mix, oysters and corn mixture. Bake at 350 degrees for 40 minutes.

Another side dish that will add something different to your Thanksgiving meal is from Ardy Tobin of San Diego. "I like it because everything comes straight off the shelf. It should be made the day before because reheating it makes the flavors mellow." ARDY TOBIN'S HOT CURRIED FRUIT (10 servings) 1/3 cup butter 1/4 to 3/4 cut brown sugar, packed 2 teaspoons curry powder 1 can (16 ounces) pear halves 1 can (16 ounces) cling peach or apricot halves 1 can (20 ounces) pineapple slices, packed in own juice 1 jar maraschino cherries with stems, or cranberry sauce

Preheat oven to 325 degrees. Melt butter in saucepan. Stir in sugar and curry. Drain fruit well on paper towels. In a 1 1/2 quart shallow casserole, layer fruit with peach halves on top. Pour butter mixture over fruit. Place a cherry or a dab of cranberry sauce in the center of each peach half. Bake at 350 degrees, uncovered for 1 hour. Cool, cover, refrigerate. Reheat next day at 350 degrees for 30 minutes.