To make yogurt you heat milk or cream to above 180°F (82.2°C), cool it down and mix with a starter culture, then let it incubate at 100°F to 120°F (37.8°C to 48.9°C) for several hours. Using a sous vide machine allows you to easily maintain the temperatures you are looking for.
Sous vide yogurt is typically made in glass mason jars with the lids either off or not fully tightened. The starter bacteria will give off gasses as they create the yogurt so a sealed container can leak or explode. The yogurt is also usually made in the container you will store or serve it from because moving it to a new one can affect the consistency of the yogurt. You can use the sous vide machine to reach both temperatures but I typically just heat the milk on the stove because it's much quicker than raising and lowering the temperature of the whole water bath.
I call for half and half, which results in a very thick yogurt. If you prefer a thinner one you can substitute whole or 2% milk. To get the incubation going you need to add a 1/2 cup of yogurt that contains live and active cultures. Yogurt that contains this type of culture will be labelled on the package. The length of the incubation time adds tanginess to the yogurt and can range from 3 hours to 24 hours.
Fill a water bath to about an inch (25mm) below the height of the mason jars you are using and preheat the water to 110°F (43.3°C).
Heat the half and half in a pot to at least 180°F (82.2°C). Remove it from the heat and let it cool to at least 120°F (48.9°C) then whisk in the yogurt with the live and active cultures. Pour the mixture into the mason jars and seal each with plastic wrap. Place the jars into the water bath and let incubate for 5 hours.
After 5 hours remove the jars from the water bath and refrigerate until chilled. Once the yogurt is cold, seal with the mason jar lids. It will last in the refrigerator for 1 to 2 weeks.
For a really interesting take on a yogurt dish you can use a whipping siphon to make a carbonated yogurt foam. Add the yogurt to a whipping siphon and fully charge with CO2. Let sit for a few hours and then dispense over fresh berries.