Split the vanilla beans but do not scrape the seeds. Pressurizing will release them.
You can cut the beans in half to ensure they are fully submerged. But if you want the beans to remain at their full length for presentation purposes simply rest the whipping siphon on its side for the two weeks.
In a 16 oz whipping siphon place the vanilla beans and vodka (or bourbon).
Seal the whipping siphon and charge with one N2O cartridge. Release about 2 seconds worth of pressure to make sure any oxygen has been released.
Charge with a second N2O charge. Allow the mixture to rest for 2 weeks.
Cover the spout and release the pressure from the whipping siphon.
Pour the mixture into a bottle for storage. Do not cap the bottle for 2 hours to let the N2O dissipate.
Use immediately or stored indefinitely.