Soften gelatin in cold water for 5 minutes.
Melt baking chocolate in top of double boiler; add boiling water and cook slowly, stirring constantly, to a smooth and thick paste.
Add sugar replacement, salt and 1/4 cup (190 mL) of the evaporated milk.
Cook and stir 5 minutes longer.
Remove from heat and add softened gelatin, stirring until gelatin is dissolved.
Cool.
Place remaining evaporated milk in a freezer tray and freeze until thoroughly chilled and edges are slightly frozen.
When chocolate mixture begins to thicken and cool, whip slightly frozen milk until stiff and fold into cooled chocolate mixture with the vanilla.
Line a decorative mold with the ladyfingers and pour the chocolate mixture into the mold.
Chill until firm; unmold onto a serving plate.