In a heatproof bowl, combine the flavored gelatin powder with 1 cup of boiling water. Whisk vigorously for about 2 minutes, or until the gelatin is completely dissolved. Make sure there are no granules left at the bottom.

Stir in the 1 cup of cold vodka. If you're using an additional 1/4 cup of liqueur for a stronger flavor, add it now. Stir well to combine.

Carefully pour the mixture into individual serving cups (typically 1-ounce or 2-ounce plastic or paper cups). Fill each cup about two-thirds to three-quarters full to avoid spills.

Place the filled cups on a tray and refrigerate for at least 2-4 hours, or until the jello shots are firm and set. You'll know they're ready when they have a solid, jiggly consistency.

Before serving, you can add a dollop of whipped cream or a small garnish if desired. Serve chilled.