Q The enclosed recipe for Ellen Well's fudge cake (from the May 1983 issue of Yankee Magazine) is delicious if it doesn't collapse in the center. Though the directions are skimpy, my first six tries were successful. I'm coming close to batting .500, however, since the centers of the last four cakes collapsed while still in the oven. What causes the center of such a cake to fall even before it's taken from the oven? A To trouble-shoot any recipe, one should convert the ingredients into weights, then compare the ratio of ingredients with those of other, similar recipes. I did that with yours and compared it with a number of recipes.

With three minor changes in ingredients, the fudge cake is identical to the Devil's Food Cake Cockaigne recipe in the "The Joy of Cooking" by Irma S. Rombauer and Marion Rombauer Becker (The Bobbs-Merrill Company Inc., 1964). The three differences are: the fudge cake recipe uses 16 ounces of brown sugar whereas the devil's food cake recipe uses 8 ounces of brown sugar and 8 ounces of granulated sugar. The fudge cake uses 12 ounces of milk whereas the devil's food cake uses 8 ounces of milk and 4 ounces of water. And the fudge cake specifies no salt (a nonessential ingredient) while the devil's food cake batter contains a half teaspoon.

Both cake recipes are very high in sugar. This makes them quite moist and soft. But it also makes their batters particularly susceptible to collapse. Sugar delays thickening of the batter's starch; as the batter heats and rises, the starch granules sink and form a dense layer at the bottom. The top layers, less dense with the loss of starch, can no longer support their weight, and the center sinks.

To prevent this from happening, I have revised your fudge cake recipe's procedures, incorporating some of the devil's food cake recipe's procedures as well as my own. I left out the vanilla as, in a baked chocolate cake, its flavor contribution is undetectable (it's better to incorporate vanilla extract into the icing). FUDGE CAKE REVISED (Makes one 9-inch cake or two 8-inch layers)

1 3/4 cups light brown sugar

2 egg yolks

1 1/2 cups milk

3 squares unsweetened chocolate

1/2 cup (1 stick butter), softened slightly, plus extra for pans

2 cups cake flour, plus extra for pans

1 teaspoon baking soda

2 egg whites

1/4 cup granulated sugar

Place 1 cup brown sugar, egg yolks, 1 cup milk and chocolate in saucepan. Heat over medium heat, stirring to prevent scorching. When all the chocolate melts and the mixture has thickened, remove and cool rapidly by setting pan in a bowl of cold water. Refrigerate this rich chocolate custard until it feels cold to the touch but has not congealed.

Cream butter and 3/4 cup brown sugar on medium speed until light and fluffy (about 10 minutes). Add the cold custard and blend, scraping sides of bowl until batter has acquired a uniform brown color. Sift flour with baking soda. Turn mixer to low speed and add flour-soda mixture alternately with 1/2 cup milk.

In a small bowl, beat egg whites on highest speed until they form soft peaks. Add half the granulated sugar. Beat until stiff peaks form. Add remaining sugar and beat again until stiff but not dry.

Using a whisk, stir 1/4 of the egg white foam into the chocolate batter. Then, using a rubber spatula, fold in the remaining foam using quick, overhand strokes, bringing the unlightened bottom batter to the surface. Pour batter into greased and floured cake pans and bake at 350 degrees approximately 25 minutes -- until a toothpick inserted in the center emerges dry and with no adhering crumbs.