Heat the Milk: Pour 1 gallon of milk into a large pot over medium-high heat. Heat the milk to 85-90°C (185-194°F), stirring very often to prevent burning on the bottom.
Simmer: Once the milk reaches the target temperature, lower the heat and let it simmer for an additional 10 minutes, keep stirring. This step helps to evaporate some of the water in the milk, concentrating the fat and resulting in a creamier, thicker yogurt.
Cool the Milk: Remove the pot from the heat and let the milk cool down uncovered but protected from contamination (like other food, dust or insects) until it reaches 40-45°C (104-113°F). This is the ideal temperature for adding your yogurt starter culture.
Add the Starter Culture: Once the milk has cooled to the appropriate temperature, add a 1/4 cup of store-bought plain yogurt or a frozen yogurt puck. Mix well to ensure the yogurt is fully incorporated into the milk.
Incubate the Yogurt: Pour the inoculated milk into your Instant Pot. Cover with the lid, set the valve to venting, and press the 'Yogurt' button. Let the yogurt incubate for 12-24 hours, depending on how tangy you want your yogurt. The longer it ferments, the tangier it becomes.
Cool and Set: After the incubation period, remove the insert from the Instant Pot, cover it, and place it in the fridge for 12 hours. This resting time allows the yogurt to cool, set, and thicken further.
Optional Strain for Thicker Yogurt: If you prefer a thicker yogurt, line a colander with cheesecloth and place it over the sink or a large dish to catch the whey. Once your yogurt has cooled, pour it into the cheesecloth-lined colander and let it strain for 30-60 minutes. This will remove some of the excess whey and result in a creamier, thicker yogurt.
Store Your Yogurt: Once your yogurt has set and thickened to your liking, portion it into jars or containers for storage. Keep the yogurt in the fridge, where it will stay fresh for about 1-2 weeks!
Optional Step for Future Batches: For future yogurt-making, make frozen yogurt pucks by filling silicone muffin molds with yogurt and freezing them. These yogurt pucks can be used as the starter culture for your next batch, saving you from buying store-bought yogurt every time!