In a small bowl, add in the gelatin and cold water. Let it set for about 10 minutes until the gelatin is bloomed. It will be completely gelled up. Set aside.
In a large mixing bowl, add in the heavy cream. Using a hand mixer, beat on medium until soft peaks begin to form.
Microwave the bloomed gelatin for 30 seconds. Make sure all of the gelatin is dissolved.
Add in the gelatin and powdered sugar and beat until stiff peaks form.
Add in the irish cream and melted chocolate. Continue to mix until incorporated. The chocolate should be about room temperature. That will help prevent the chocolate from melting the whipped cream mixture.
Add the mousse into a piping bag and pipe into dishes.
Place in the fridge and let set up for at least an hour. Serve!