Turn the Ninja Foodi Deluxe "on."Choose the "yogurt" function. (Be sure that the screen says yogurt and not "hi.")
Pour in ½ gallon of milk. Do not add in yogurt, flavors or sweeteners. Only the milk should be added in this step.
Close the "pressure cooker" lid and move valve to "vent."
Push the start button. The screen should say "yogurt" and be set to a time of 8:00.
Milk will boil in the pot during the initial cooking time. Once the milk has reached a boil, the Ninja Foodi Deluxe will beep and the screen will say "boil" on it. This step should take about an hour.
After the milk has boiled, it will need to cool. The Ninja Foodi Deluxe will automatically change to the "cool" mode. The milk will cool for about an hour or so. Don't panic if it does take longer.
Once the milk has cooled, the Ninja Foodi Deluxe will beep and the screen will say "add and stir." When this happens, open the "pressure cooker" lid.Add in 2 tablespoons of yogurt (the yogurt must have active yogurt cultures).
Whisk the milk and yogurt together with a plastic or silicone whisk. Do not use a metal whisk as this will scrape the pot.
Replace the "pressure cooker" lid and make sure valve is set to "vent" position.
Push start button again to get the Ninja Foodi Deluxe going again.
The screen should now say "incubate" and be set to 8 hours.Let the yogurt incubate. When the timer beeps, remove the lid and check to make sure that the yogurt has set up. You can do so by stick a spoon in the middle of the yogurt. The spoon should stand up on it's own.
Refrigerate yogurt for at least 4 hours.
Add in honey and vanilla extract or vanilla bean paste. Stir until well combined.
Place into mason jars or whatever food storage containers you prefer.
Notes
Do not add honey to the yogurt until you have completed the incubation period and have refrigerated the yogurt for a couple of hours.
Be sure that you are actually using the "yogurt" function and not the "slow cook" option.
Be patient! If the yogurt does not set up quite as much as you would like, continue to incubate it longer. You can continue to incubate before you reach the refrigeration step.