Get you removable spring form pan (or cake pan) ready. Line the 6 or 7 inch pan with parchment circle to fit the bottom and parchment to fit the sides of the pan. Or you can line the entire cake pan with cellophane leaving an overhang to be able to lift the Charlotte out. Set aside.
In a stand mixer bowl, cream together the butter and sugar using whisk attachment, on medium for a few minutes and until combined. Add the cooked egg yolks and continue to cream together. Add the melted chocolate beating on high to until smooth. Add the heavy cream, beating until fluffy. Add the rum and the vanilla.
For the bottom of the pan, next pour the ¼ cup of rum into a flat bowl. Dip a ladyfinger into the rum for a few seconds, turning over to dip the other side, then lay in your parchment or cellophane lined pan. Continue to dip and lay the ladyfingers like this, breaking them as needed to fit into the bottom of the pan. Be sure to leave a ½ inch edge around the pan to fit the ladyfinger that will stand on its edge. Fill the center with the cream and smooth, bringing over the touch the insides of the ladyfingers. Top with berries.
Cover with cellophane and refrigerate for 4 hours or until chilled.
Remove the Charlotte by either removing the bottom of the spring pan or pulling up on the cellophane gently the cake pan does not have a removable bottom. Plate and decorate with a ribbon and a dusting of powdered sugar or cacao powder.