Pour the milk into your clean Instant Pot inner pot. Secure the lid and set the valve to 'Sealing'. Press the 'Yogurt' button and select 'Normal' or 'Boil' (if your model has it) and let the milk heat for about 10-15 minutes, or until it reaches 180°F (82°C). If your pot doesn't have this function, you can manually heat the milk on the stovetop to this temperature.

Once the milk has reached 180°F, carefully remove the inner pot from the Instant Pot base. Let the milk cool down to 110-115°F (43-46°C). You can speed this up by placing the inner pot in an ice bath, stirring occasionally. Alternatively, you can leave the lid on and let it cool naturally. It's crucial to reach this temperature range for proper culturing.

In a small bowl, whisk together the 1/2 cup of starter yogurt with a ladleful of the cooled milk until smooth. This helps temper the cultures.

Pour the tempered yogurt mixture back into the main pot of cooled milk. Whisk gently to combine thoroughly. If you plan to add sweetener or flavorings now, do so at this stage and whisk well.

Place the inner pot back into the Instant Pot. Secure the lid and set the valve to 'Sealing'. Press the 'Yogurt' button and select 'Incubate' or '8 Hours' (or your desired fermentation time, typically 8-12 hours). Ensure the lid is sealed and avoid disturbing the pot during this time.

Once the incubation cycle is complete, carefully open the lid. The yogurt should look thickened. You can strain it further for a thicker consistency (like Greek yogurt) by lining a sieve with cheesecloth and letting it drain over a bowl in the refrigerator for a few hours. Discard the whey or save it for other uses.

Transfer the finished yogurt to airtight containers. Chill thoroughly in the refrigerator for at least 4-6 hours before serving to allow it to set completely.