Two 1 quart jars with lids
A fine-weaved dish towel
Small cooler, optional
Pour milk into a saucepan and bring the temperature up to 185 degrees Fahrenheit over low-medium heat. It’s important to not boil the milk because doing so can change the structure and taste. I recommend using a thermometer for accuracy because stoves vary a lot. Don’t stir your milk while it’s heating.
Remove milk from heat and allow it to cool to about 115 degrees Fahrenheit. You can do this more quickly by covering the pot and placing it in a larger pot or sink full of ice water.
Once the temperature has cooled, measure out one cup of the warm milk into a separate bowl. Whisk 4 tablespoons of your starter into the separate bowl to allow it to activate, then add the contents into the large pot of milk. Whisk well.
Next, you’ll allow your yogurt to culture. Transfer the milk mixture into a 1 quart jar and secure it tightly with a lid. To be sure that your yogurt stays warm and cozy, you can do one of two things: 1) You can place the yogurt in a consistently-warm room in your home (such as a laundry room) or 2) You can create such a spot for it. You can do this by filling another 1-quart container with hot water, covering it with a lid, and placing it, along with the yogurt-filled container, in a small cooler. You can even wrap both of these jars in a towel for good measure. Be sure that the cooler and contents are in the warmest room of your house.
Check your yogurt after about 12 hours, but note that it can take longer using this more hands-on method (as opposed to a yogurt-machine method). I let mine ferment for 24 hours before moving it to the fridge. The yogurt should be firm, but jiggly to the touch. It will continue to firm in the fridge, but note that this method will typically produce a looser consistency. If you’d like to firm up your yogurt, you can do so by lining a colander with cheesecloth or a fine-weave dishcloth and placing it above a large bowl. Next, put the yogurt into the cloth-lined colander and let it sit for a few hours in the refrigerator. You’ll want to discard the liquid that strains out and transfer the finished yogurt into a separate container.