If fudge doesn't harden and is very, very runny, turn it into a Bavarian Cream.
Take 1/2 cup runny fudge and sprinkle gelatin over it. Allow to sit until gelatin softens and swells. Dissolve gelatin completely by microwaving on medium (50%) for 15 to 30 seconds, or by placing over hot water. Mix warmed fudge back into the rest of fudge and let cool to room temperature. Beat egg whites, adding cream of tartar when they become frothy. Continue beating to stiff peaks, and fold into fudge mixture. Beat cream in chilled bowl using chilled beaters until stiffened but not thick-it should hold soft peaks-and fold into fudge mixture. Pour into 6-cup mold and chill until ready to serve.