1. Arrange the plastic shot cups on a rimmed baking sheet or tray so they are easy to move, or stand the plastic syringes upright in a jar or glass.

2. Add the orange flavored gelatin dessert mix to a medium heatproof mixing bowl.

3. Carefully pour in the boiling water while whisking continuously and stir for about 2 minutes, until the gelatin granules are completely dissolved and the mixture looks clear.

4. Stir in the cold water to help cool the mixture slightly.

5. Add the vodka and the orange liqueur, if using, and whisk until everything is well combined.

6. Taste a tiny spoonful of the warm mixture and adjust by adding a splash more cold water for a softer shot or a small splash more vodka for a stronger shot, keeping the total liquid level the same so the shots will still set.

7. Use a small pourable measuring cup or squeeze bottle to carefully fill each plastic shot cup about three-quarters full with the gelatin mixture.

8. If using plastic syringes, place the syringe tips into the gelatin mixture, slowly draw the liquid up, and stand them upright so they do not spill.

9. Transfer the tray of shot cups or the container of syringes to the refrigerator and chill for at least 3 to 4 hours, or until the jello shots are fully firm and set all the way through.

10. Just before serving, top each jello shot with a swirl of whipped cream and a pinch of Halloween sprinkles or a candy eye.

11. Serve the shots well chilled straight from the refrigerator and enjoy within a few days for the best texture and flavor.