Preheat oven to 350 degrees F (175 degrees C). Line a 17-1/2x11-1/2 inch jelly roll pan with foil leaving a 2 inch overhang on short sides, fold overhang under the pan. Spray with foil with non-stick cooking spray and dust with flour. Tap out any excess flour.
In the top of a double boiler over hot, not simmering, water, melt the chocolate with the coffee stirring until smooth. Remove from double boiler and cool about 10 minutes until tepid.
Separate the eggs. With an electric mixer beat the egg yolks at medium speed until blended. Add 1/2 cup sugar in slow steady stream, beating. Increase speed of mixer to medium high and continue beating 3 - 5 minutes until pale yellow and tripled in volume. Beat in the tepid chocolate mixture and vanilla until blended.
Beat egg whites until frothy, increase speed of mixer and beat until soft peaks start to form. Add the remaining 2 tablespoons of sugar and beat until stiff peaks.
Fold 1/3 whites into egg yolk/chocolate mixture to lighten it. Fold in remaining whites gently, don't over fold or you'll deflate the cake.
Spread batter into prepared pan and bake at 350 degrees F (175 degrees C) for 12-15 minutes or until a toothpick comes out clean or cake springs back when gently touched in center.
Run knife around edges of pan, invert on clean kitchen towel. Peel off foil and starting on one long side roll the cake with towel into long cylinder. Cool on a rack for 20 minutes. When cool spread with mousse or whipped cream or pudding mixed with whipped cream and roll up again. Dust with cocoa if desired or powdered sugar. Great served with raspberries on the side as garnish.