In a double boiler, add semisweet and milk chocolate chips, dark coffee, shortening, and rum. Stir constantly until everything is melted and incorporated.
Remove from heat and let cool. I placed mine in the fridge to cool quickly.
In a small microwave-safe bowl, add ¼ cup of heavy cream and unflavored gelatin. Let it bloom for 10 minutes.
Place the bowl of cream and gelatin in the microwave for 15-20 seconds to melt the gelatin. Do not boil the gelatin.
Add the gelatin mixture to the cooled chocolate mixture. Stir until combined.
In a stand mixing bowl, pour in the ¾ cup of heavy cream that is left. Whip with the whisk attachment on high until the mixture comes to stiff peaks.
Fold a small portion of the cream into the chocolate mixture.
After the chocolate is lightened up, add the rest of the whipped cream and fold carefully.
Spoon into serving dishes and chill for an hour. I chilled mine in the bowl for a few hours and then placed it in a piping bag to be piped.