At least 3 hours before serving
Preheat a water bath to 140°F (60°C).
Lightly scrub the outside of the oranges then remove the zest with a vegetable peeler. Make sure little to no pith came off as well, using a paring knife to remove any. The orange pieces can be reserved for garnishing the drink. Split the vanilla bean in half.
Combine all the ingredients in a sous vide bag or mason jar then seal and place in the water bath. Heat the infusion for 1 to 2 hours.
Prepare an ice bath with 1/2 ice and 1/2 water. Remove the bag or mason jar from the water bath and place in the ice bath for 15 to 20 minutes. Strain the vodka and store in a sealed container.
Fill a cocktail shaker with ice. Add the orange-vanilla vodka, orange juice, and half and half to the shaker. Shake vigorously for 15 seconds, until everything is combined well. Strain into a martini glass and garnish with an orange slice.
For a really playful presentation I like to make a creamy orange foam to top the drink. Place 1.5 cups orange juice in a pot and add 3.5 grams of gelatin, or about 2 gelatin sheets. Let the gelatin bloom for 5 to 10 minutes.
Once bloomed, heat the pot over medium heat while stirring until the gelatin dissolves. Remove from the heat and stir in 1/4 cup of half and half. Pour the mixture into a whipping siphon, seal and charge it fully. Place the siphon in the refrigerator for at least an hour or two to let the gelatin set completely. The foam can be stored in the refrigerator for several days. Dispense the foam on top of the creamsicle when serving.