Sanitize Your Instant Pot: Begin by ensuring your 6 or 8-quart Instant Pot's stainless steel inner pot, lid, and sealing ring are scrupulously clean. Wash thoroughly with hot soapy water, rinse well, and dry with a clean cloth. This critical step eliminates any unwanted bacteria that could interfere with your yogurt culture.

Heat the Milk (Boil Function): Pour the 8 cups of milk into the sanitized Instant Pot inner pot. Secure the lid, leaving the pressure release valve in the 'Venting' position (or use a glass lid if preferred). Press the 'Yogurt' button, then toggle until 'Boil' appears on the display. Press 'Start'. The Instant Pot will heat the milk to approximately 180-200°F (82-93°C) over 25-40 minutes, denaturing proteins and killing existing bacteria for a fresh start. Once finished, the Instant Pot will beep.

Cool the Milk to 110-115°F: This is a crucial temperature-sensitive step. Carefully remove the inner pot from the Instant Pot. Insert an instant-read thermometer into the milk. Allow the milk to cool naturally on the counter until it reaches 110-115°F (43-46°C). For a quicker cool, place the inner pot in an ice bath in your sink, stirring occasionally, until the target temperature is reached (about 10-15 minutes). Cooling to this precise range prevents killing your starter cultures (too hot) or failing to activate them (too cold).

Temper and Add the Yogurt Starter: Once the milk has cooled, dry the exterior of the inner pot if you used an ice bath. In a small bowl, ladle about 1 cup of the warm milk and whisk in the 2 tablespoons of live culture yogurt starter until completely smooth. This tempering step prevents shocking the delicate cultures. Gently pour this mixture back into the main pot of milk and whisk briefly to combine thoroughly. Avoid over-whisking.

Incubate for Creamy Perfection: Return the inner pot to the Instant Pot. Secure the lid again, ensuring the pressure release valve is set to 'Venting'. Press the 'Yogurt' button once more, then adjust the time to your desired incubation period, typically 8 to 12 hours. Press 'Start'. Less time yields milder yogurt, while longer incubation (up to 12 hours) produces a tangier, thicker yogurt with more active cultures. The Instant Pot will count up as it incubates, maintaining the ideal temperature for bacterial growth. Do not disturb the pot during this time.

Chill to Set: Once the incubation cycle is complete, the yogurt will appear jiggly and set like a soft custard. Gently remove the inner pot, cover it loosely with plastic wrap or a lid, and refrigerate for at least 4 hours, or preferably overnight. Chilling allows the yogurt to firm up further and fully set its texture, preventing a runny consistency.

Optional: Strain for Greek Yogurt: For thicker, Greek-style yogurt, line a fine-mesh sieve with cheesecloth and place it over a large bowl. Pour the chilled yogurt into the lined sieve. Cover and refrigerate while it strains. Strain for 2-4 hours for standard Greek yogurt, or overnight for an even thicker, more labneh-like consistency. The liquid collected in the bowl is whey, which can be saved for smoothies or baking.