Important: Before starting, be sure to follow safe fermentation practices and ensure your equipment is clean and temperatures are accurate. See Notes.

Blend or whisk 1 cup of soy milk with the pea protein powder in a bowl. Let the mixture sit for 5 to 10 minutes to hydrate the protein, then whisk again until smooth.

Pour the hydrated mixture into a 5-quart Dutch oven along with the remaining 3 cups of soy milk. Set the pot over medium-low heat and gently warm the mixture to 180–195°F. Avoid letting it boil. Hold the temperature for a few minutes, then remove the pot from heat.

Let the mixture cool to approximately 120°F. If a skin forms on top, remove and discard it.

While the milk cools, preheat your oven by turning on the “Keep Warm” function for about 5 minutes. Then turn it off. The goal is to bring the oven cavity to around 120-125°F.

In a small bowl, whisk together 1 cup of the cooled soy milk mixture with ¼ cup of room temperature yogurt starter (such as Siggi’s Plant-Based Yogurt).

Add the starter mixture back into the remaining cooled milk in the Dutch oven. Mix well to combine. The mixture should now be around 115–120°F.

Cover the Dutch oven with its lid and place it into the pre-warmed oven. Make sure the “Keep Warm” function is turned off and the oven light is on to maintain warmth.

Let the yogurt culture for 4 to 6 hours. For the first hour, aim to keep the temperature between 115–120°F. After that, it should stay between 108–115°F. Check periodically. If the temperature drops too low, briefly turn on the “Keep Warm” setting for 3 to 5 minutes, then turn it off again. Do not leave it on continuously, as high heat can kill the cultures.

Once fermentation is complete, optionally strain the yogurt for a thicker, Greek-style consistency. Line a sieve with cheesecloth and place it over a bowl. Transfer the yogurt to the sieve and strain in the fridge for at least 30 minutes or overnight.

After straining, whisk or blend in vanilla bean paste or other flavorings of your choice. Whisking preserves a thicker texture, while blending will make it slightly looser.

Scoop or pipe the finished yogurt into sterilized jars. Store in the fridge for up to 2 weeks. Makes roughly a 450-500 gram batch.→ Once you make your first batch, be sure to reserve ~½ cup to use as the starter for future batches. This is enough for 8 cups of milk (or a double batch). Use the starter within 5-7 days.