Step 1

Stir together coffee and coffee liqueur in a small bowl. Sprinkle evenly with 1 pack of the gelatin; let stand until bloomed, about 1 minute. Pour 1/2 cup of the hot water over mixture, and whisk until gelatin is dissolved, about 1 minute. Pour 1 ounce (2 tablespoons) coffee mixture into each of 8 shot-sized plastic cups. Refrigerate until set, about 30 minutes.

Step 2

Combine Irish cream liqueur and pecan liqueur (if using, if not, use equal amounts of Irish cream liqueur) in a small bowl. Sprinkle with 1 packet of the gelatin; let stand until bloomed, about 1 minute. Pour 1/2 cup of the hot water over mixture, and whisk until gelatin is dissolved, about 1 minute. Pour 1 ounce (2 tablespoons) Irish cream mixture on top of gelatinized coffee layer. Refrigerate until set, about 30 minutes.

Step 3

Pour Irish whiskey into a small bowl. Sprinkle with remaining 1 gelatin packet; let stand until bloomed, about 1 minute. Pour remaining 3/4 cup hot water over whiskey, and whisk until gelatin dissolves, about 1 minute. Pour 1 ounce (2 tablespoons) whiskey mixture over gelatinized Irish cream layer. Refrigerate until set, 45 minutes to 4 hours.