Several weeks ago, watching Tom Snyder's TV show "Tomorrow," I saw what must have been one of the great culinary mishaps of all time. Three great chefs tried to demonstrate three interesting dishes -- without much success.

The first, George Perrier from Philadelphia's fabulous LeBec-Fin, was prepared to show a nouvelle cuisine salad. On a mound of mixed greens, he sprinkled a good handful of chopped Scotch salmon (at $19 a pound), then sauteed and flambeed a handful of tiny bay scallops (at only $8 a pound) and finally poured the hot crayfish tails and scallops, sauced with flaming brandy, over the cold lettuce and chopped salmon.

As the chef tried to finish his esoteric task, Snyder kept interrupting under the pretext of "participation," going so far as to hold his gasoline-fueled cigarette lighter in the cognac to ignite it. (What an added taste, what a fragrance!)

Then the owner-chef from Tony's of Houston tried to sautee tenderloin in a cold pan over a cold stove -- someone had forgotten to turn on the heat before the program began.

Then came my dear friend and colleague, Paul Prudhomme from the Commander's Palace in New Orleans. He wanted to demonstrate his whimsical and delicious Cajun Chocolate Cottage filled with Louisiana strawberries. Paul is not only a great chef and an excellent conversationalist but also a very accomplished demonstrator.

This is a tricky dessert. You melt some fine eating chocolate, then cool it and cut the parts of a simply Cajun cottage from the chocolate sheets. Then you assemble it and "glue" it with melted chocolate, fill the cottage with strawberries, and add the roof.

Then comes the showmanship. You ladle a boiling hot sabayon sauce over the chocolate cottage. It melts instantly to reveal the vivid red strawberries, surrounded by melted chocolate and hot sabayon.

I have seen Prudhomme dazzle a large crowd with this Cajun cottage, but on Snyder's show it just wouldn't work. No matter how much sabayon he ladled on the chocolate cottage, it wouldn't melt. Chef Paul, never at a loss for words, smiled at the host and exclaimed, "This will soon be a Louisiana flood! But the cottage still would not melt. Why? Because Snyder had removed the double boiler of the sabayon from the heat of the stove earlier in the program -- it was in his way. He sabotaged Chef Paul's demonstration.

I switched off my TV set and thought how fortunate I was, with all the shows I have done, never to have run into this kind of disaster. One of my favorite demonstrations has never caused a moment of concern. I refer to gateau Allard, a fabulous spring and summer cake which is very popular in France. It is easy to make now, in a slightly Americanized version, because raspberries here enjoy a much longer season than in France, and their quality this year is excellent and the price tolerable. GATEAU ALLARD (A modern American version) 1 round loaf French or Italian bread, 1 to 1 1/2 pounds, preferably unsliced 1 cup water 4 to 6 tablespoons sugar 2 half-pint containers fresh raspberries 4 cups sour cream or sour half-and-half 2 to 3 tablespoons brown sugar

With a very sharp knife, carefully remove crust from bread. Cut 5 to 6 slices, cutting horizontally so you get large, round slices like cake layers.

Use a 1 1/2-to 2-quart Charlotte mold or simply a small pot which measures about 5 inches at bottom, 6 inches at top and 4 inches deep. Line mold or pot with plastic that overhangs at top on all sides. With kitchen scissors, cut round bread slices to fit mold.

(If you bought pre-sliced bread, remove crust and reassemble slices to fit mold in pairs. When you make gateau, alternate layers so that slices join at different angles.)

When you have all your bread ready, cover bread slices with a towel to prevent drying.

Bring water with sugar to a boil. After 1 or 2 minutes, remove and cool to lukewarm. Add 1/2 pint raspberries and gently press with a fork to a loose raspberry syrup. Add remaining 1/2 pint raspberries, leaving out 8 berries for decoration.

Set 1 cup sour cream aside. Fold brown sugar into remaining 3 cups with a rubber spatula. Don't overmix -- sour cream should be fairly firm.

Using sugared sour cream, spread one side of one layer of bread. Place bread, sour cream-side up into mold. Spoon 2 to 3 tablespoons of raspberry filling evenly on top.

Now spread sour cream on both sides of next layer and gently press it over berries. Spoon in filling and continue until you get to last layer of bread. Add all remaining rasperry mixture, spread last layer of bread with sour cream on one side only, and press bread on filling, sour cream-side down.

Cut a round cardboard just a bit smaller than last layer of bread, cover it with aluminum foil, and gently, evenly press it into mold. Bring plastic liner up over cardboard, place a light weight on top and refrigerate gateau at least overnight or as long as 2 days.

Before serving, open plastic sheet, put a serving platter over top of mold, Turn upside down, and lift off mold and plastic. Cover sides and top of gateau with 1 cup reserved sour cream. If you wish, sprinkle some brown sugar on top (it will start to melt and make an interesting pattern). Decorate with 8 reserved raspberries.

Serve, spooning some of remaining sugared sour cream on each serving. Serves 8 to 10.

Variation: You may prepare the same cake with sliced strawberries, over-ripe peaches or ripe apricots. Of course, you can also use frozen raspberries, a combination of frozen and fresh raspberries or a combination of strawberries and fresh raspberries.

This gateau is ideal for persons who want to avoid sugar. Instead of using brown sugar, you can mix a little sweetener into the sour cream and sweeten the same way. If you like a juicier, moister cake, increase the liquid with 1/3 or 1/2 cup more water.