Place an upside-down strainer or bowl in your water bath. Top with a baking sheet or plate. Set the ramekins on the baking sheet and fill the water bath two-thirds of the way up the ramekins. Preheat the water bath to 87°C.
Pour the heavy cream into a pot. Split the vanilla bean and scrape out the seeds, then add the seeds and the bean to the cream. Add the cinnamon stick. Bring just to a simmer, stirring frequently. Turn off the heat and let it infuse for 10 minutes. Strain the cream.
Whisk together the egg yolks in another bowl, then slowly whisk in the salt and sugar. The mixture should turn glossy and thicken slightly. Slowly whisk in the infused cream.
Evenly divide the mixture among the ramekins, cover each ramekin with plastic wrap, and use a rubber band to hold it in place. Place the ramekins in the sous vide bath with the water level coming two thirds of the way up the side. Cook for 60 to 90 minutes, depending on how thick you prefer your crème brûlée.
Once cooked, remove the ramekins from the water bath and let the crème brûlée cool for 15 to 20 minutes. Place in the refrigerator and chill until firm, or preferably overnight.
To Assemble: Spread a thin layer of sugar a few grains thick on the top of each crème brûlée and quickly torch until the sugar melts and begins to brown. Add a few mint leaves and serve.