Prepare the Panna Cotta:

1. Place the cold water in a small bowl. Evenly sprinkle the gelatin over the water and let it stand until the gelatin is absorbed.
2. In a small saucepan, heat the eggnog over medium heat until it’s hot but not boiling. Remove from heat and add the gelatin mixture, stirring until the gelatin is completely dissolved.
3. Arrange six 4-ounce dessert glasses on a baking sheet. Pour approximately ⅓ cup of the eggnog mixture into each glass.
4. Transfer the baking sheet with the glasses to the refrigerator and chill for at least 2 hours, or until set.

Prepare the Spiked Cranberry Sauce:

1. In a medium saucepan, combine the cranberries, sugar, orange zest, and orange juice. Bring to a boil over medium-high heat.
2. Once the cranberries begin to pop, reduce the heat to a simmer. Use the back of a spatula to mash the berries against the bottom of the pan. Continue cooking until the mixture reaches a jam-like consistency.
3. Remove from heat and stir in the orange liqueur. If the sauce is too thick, add water 1 tablespoon at a time until the desired consistency is achieved. Let the sauce cool, then refrigerate until ready to use.

Assemble the Dessert:

1. Once the panna cotta is firm, spoon the cranberry sauce on top of each serving, filling to the brim of the glass.
2. For garnish, skewer each cranberry completely through with a toothpick, then thread a rosemary sprig through each berry. Place the garnish atop each glass.
3. Cover and refrigerate until ready to serve.