Prepare a sponge cake in a 13in. x 18in. sheet cake pan. Using the rim of the dessert cups or a cookie cutter, cut out small circles from the sponge cake.
In a large mixing bowl, combine the heavy whipping cream with the Bailey's. Place a sponge cake round in the bottom of each dessert cup and pour a spoonful of the cream over each one.
Make the Chocolate Mousse
Into a separate large bowl, combine the chocolate chips, coffee, and second portion of Bailey's. Microwave the mixture for 1-2 minutes, stirring every 30 seconds until it's completely melted.
In a separate small bowl, combine 1/4 cup of the heavy whipping cream and one teaspoon of the gelatin and allow it to soften at room temperature for 5 minutes. Then, microwave the mixture for 5 seconds and stir it until it turns runny in texture. Add the gelatin mixture into the chocolate mixture and stir to combine.
Beat the other 1 and 1/2 cups of very cold heavy whipping cream with a hand or stand mixer until you get stiff peaks.
Stir in half of the whipped cream into the chocolate mixture. Next, fold in the remaining whipped cream, being extra careful not to overwork the mousse.
Assemble the Dessert Cups
Carefully stuff the chocolate mousse into a piping bag and pipe equal amounts of the mousse on top of each sponge cake layer. Optionally, top the mousse with another sponge cake round, followed by another layer of mousse if you're using taller dessert cups.
Garnish each dessert cup with shredded chocolate or cacao powder. Keep the cups refrigerated until you plan to serve them. Enjoy!