Adjust rack one-third up from bottom of the oven and preheat oven to 350 degrees. You will need a round cake pan 8 inches in diameter and 3 inches deep, or a 2-1/2-quart soufflé dish (8 x 3-1/2 inches). Cut a round of wax paper to fit the bottom. Butter the sides of the pan or dish and one side of the paper. Place the paper, buttered side up, in the pan. Shake a bit of flour into the pan, tap it around to coat all surfaces, then invert the pan to remove excess. Set pan aside.

Sift the flour and sugar together and set aside. Place the chocolate in the top of a large double boiler over hot water on moderate heat. Dissolve the coffee in the boiling water and pour over the chocolate. Cover the pot and leave until the chocolate is melted. Remove the top of the double boiler and stir well with a wire whisk until smooth. With the whisk gradually stir in the butter, adding about a 1/2-inch slice at a time and whisking until smooth after each addition. Gradually whisk in the dry ingredients and then the rum.

Place the egg yolks in a large mixing bowl and stir them lightly with the whisk just to mix. Gradually add the warm chocolate mixture, stirring well to mix.

Add the salt to the egg whites and beat until they just hold a shape or are stiff but not dry. In two or three additions fold the whites into the chocolate.

Pour the mixture into the prepared pan. Smooth the top. Place the prepared pan in a larger but not deeper pan, and pour in hot water to reach about halfway up the sides of the cake pan or soufflé dish.

Bake for 1 hour and 10 minutes. Remove the smaller pan from the hot water and place on a rack to cool to room temperature (it will take 1 hour or more but it may stand overnight). The cake will shrink as it cools-don't worry. (The cooled cake will be about 1-1/2 inches high.)

With a small, sharp knife cut around the sides to release. Cover with a flat cake plate or a serving board, centering the plate evenly over the cake. Invert the plate and the cake pan. (If it doesn't lift off easily, bang the plate and the pan gently against a table or counter top.) Remove the pan and peel off the paper lining.

I think this cake is best at room temperature. Therefore it should be covered with the whipped cream immediately before serving. But if that is too much of a hassle, put the whipped cream on ahead of time and refrigerate the cake until serving time. (It is really divine either way.)

Whip the above ingredients until they are stiff enough to hold a shape when spread over the cake. With a small metal spatula first cover the sides of the cake and then the top. The cream may be spread smoothly or swirled into peaks.

The whipped cream may be left as is or decorated with chocolate curls or with candied violets or rose petals. (The violets or rose petals should be put on at the last minute or they might discolor the cream.)

Refrigerate.