Sprinkle 1/2 package unflavored gelatin into a heat-resistant bowl and pour boiling water on top, stirring to dissolve. Add Irish cream liqueur and stir until well incorporated. Fill shot glasses halfway and refrigerate until set, 2 to 4 hours. Sprinkle remaining 1/2 package unflavored gelatin into a heat-resistant bowl and pour boiling coffee on top, stirring to dissolve. Add Irish cream liqueur and stir until well incorporated. Pour coffee mixture into the half-filled shot glasses on top of the previous layer. Return to the refrigerator and chill until set, 2 to 4 hours.