Pour 1/2 cup of A2 milk into a glass bowl and the remaining milk into a stainless steel Instant Pot. Cover the Instant Pot and set it aside for 1 hour.
In the glass bowl, add 1/2 cup of A2 yogurt to the 1/2 cup of A2 milk and stir gently by hand to combine. Let the yogurt and milk mixture sit for 30 minutes to reach room temperature (do not microwave, as this will kill the cultures).
In a separate glass bowl, combine all the dry ingredients and stir by hand to mix thoroughly.
Slowly pour the dry ingredients into the wet yogurt and milk mixture while continuing to stir by hand. Once well combined, cover with a lid and let it sit for another 30 minutes at room temperature.
In the stainless steel Instant Pot containing the A2 milk, add the probiotic mixture and stir gently to combine.
Place the lid on the Instant Pot, set it to the Yogurt function on low heat, and set the timer for 36 hours. Start.
The first batch of L. reuteri yogurt has been made. You may notice that the liquid (whey) has separated from the solids (curds). To remedy this, use 1/2 cup of the yogurt along with a tablespoon of inulin and/or other fructooligosaccharides (FOS) to create a second batch.