Heat the plant milk. Pour the milk into a Dutch oven and place over medium to medium-high heat. Warm the plant milk to right below boiling, about 200°F. Stir the plant milk gently as it heats to make sure the bottom doesn't scorch and the plant milk doesn't boil over. According to the National Center for Home Food Preservation, this heating step is necessary to change the protein structure in the plant milk so it sets as a solid instead of separating.

Cool the plant milk. Let the plant milk cool until it is just warm to the touch, 112°F to 115°F. Stir occasionally to prevent a skin from forming. (Though if one does form, you can either stir it back in or pull it out for a snack!) You can help this step go faster by placing the Dutch oven in an ice water bath and gently stirring the plant milk.

Thin the plant yogurt with plant milk. Scoop out about a cup of warm plant milk into a bowl. Add the plant yogurt and whisk until smooth and the yogurt is dissolved in the plant milk.

Whisk the thinned plant yogurt into the plant milk. While whisking gently, pour the thinned plant yogurt into the warm plant milk. This inoculates the plant milk with the plant yogurt culture.

Transfer the pot to the (turned-off) oven. Cover the Dutch oven and place the whole pot in a turned-off oven — turn on the oven light or wrap the pot in towels to keep the plant milk warm as it sets (ideally around 110°F, though some variance is fine). You can also make the plant yogurt in a dehydrator left at 110°F or using a yogurt maker.

Wait for the plant yogurt to set. Let the plant yogurt set for at least 4 hours or as long as overnight — the exact time will depend on the cultures used, the temperature of the plant yogurt, and your plant yogurt preferences. The longer plant yogurt sits, the thicker and more tart it becomes. If this is your first time making plant yogurt, start checking it after 4 hours and stop when it reaches a flavor and consistency you like. Avoid jostling or stirring the plant yogurt until it has fully set.

Cool the plant yogurt. Once the plant yogurt has set to your liking, remove it from the oven. If you see any watery whey on the surface of the plant yogurt, you can either drain this off or whisk it back into the plant yogurt before transferring to containers. Whisking also gives the plant yogurt a more consistent creamy texture. Transfer the to storage containers, cover, and refrigerate. Homemade plant yogurt will keep for about 2 weeks in the refrigerator.

Your next batch of homemade yogurt. Once you start making your own yogurt, you can use some of each batch to culture your next batch. Just save ½ cup to use for this purpose. If after a few batches, you notice some odd flavors in your yogurt or that it's not culturing quite as quickly, that means that either some outside bacteria has taken up residence in your yogurt or that this strain is becoming weak. As long as this batch still tastes good to you, it will be safe to eat, but go back to using some store-bought commercial yogurt in your next batch.