• Pour milk into a stockpot and heat to 180ºF over medium heat, stirring occasionally. This heat treatment kills any bacteria that may be in the milk; they can compete with the “good” bacteria introduced with the starter. 
  1/2 gallon milk
• Once temperature is achieved, remove from heat and allow to cool to about 125ºF. Whisk in honey and vanilla if using. 
  1/4 cup honey, 1 tablespoon vanilla
• Continue monitoring temperature. When the mixture reaches 108°F to 112°F, whisk in the starter yogurt until it’s completely incorporated. It’s important not to add the yogurt too early, as high temperatures can kill the active cultures. 
  6 ounces yogurt
• Pour mixture immediate into jars and incubate for 6-8 hours. Do not disturb the jars while they are incubating.

How to incubate yogurt:

• Insulated cooler: This is my go-to method and easy to do. I like to put a couple of jars of hot water inside a lunch-sized cooler to pre-warm it before putting the jars of prepared yogurt inside. When the yogurt is ready, add them to the cooler and secure the lid. If your cooler isn’t well insulated, you can wrap it in a towel to help retain the heat.
• Oven: If your oven has a bread proofing setting, that’s perfect for incubating yogurt. If not, turn the oven on to warm before placing jars of yogurt inside to incubate, then turn the oven on for short bursts every 1/2 hour or so to help maintain the warm environment. The pilot light on a gas stove may be sufficient to maintain the temperature.
• Slow cooker: Heat the milk and make the yogurt directly in the slow cooker. When ready to incubate, wrap the slow cooker in a bowl for insulation. The  heat  of the crock will help hold it at the right temperature. 
• Instant Pot: Many of the newer models of electric pressure cookers have a variety of settings. If yours has a yogurt setting, set jars inside and follow manufacturer’s instructions. 
• Yogurt machine: This is a specialized appliance just for making yogurt at home. Follow manufacturer’s instructions.