Soak gelatin in 1/3 cup water. Heat until dissolved. Cool.
Peel, seed and cut chirimoyas in small pieces. Sprinkle lemon juice.
Whip eggs until stiff. Gradually add sugar and continue beating until thick and glossy and stiff peaks form when whisk is lifted.
Reduce speed and add gelatine and chirimoya.
Pour into moistened tube pan. Refrigerate 4 hours.
To unmold, place pan over hot water a few seconds and invert immediately on a serving platter.
Drizzle chocolate fudge on top and serve rest of sauce in a sauceboat.