In a large mixing bowl, combine 4 packets of the gelatin with 1 ½ cups hot water.
Mix well until all the gelatin clumps are dissolved.
Add the Guinness and give a light stir.
Line your glasses up on a baking sheet or something flat that will be easy to transfer to the fridge.
Fill each shot glass about ¾ of the way full. Chill for 1 hour or until set.
Combine the remaining hot water and gelatin packet in a medium mixing bowl and mix until all gelatin clumps have dissolved.
Add the vodka and Kahlua. Mix using the hand mixer until about half of the mixture is frothy.
Using your injector, suck up just the frothy layer and dispense it on top of each jello shot until it’s full. About halfway through, mix your remaining mixture until it’s frothy again and finish filling the glasses.
Chill the shots for another hour or until set. Enjoy!