For homemade cocoa yogurt with stevia, first mix stevioside and inulin. Less of this mixture is needed for the yogurt, just store the rest in a well-sealed container.
Preheat the oven to 40 °C. Bring the milk to 45 °C. Mix all the ingredients with the milk and pour into clean jars. Leave in the switched-on oven overnight without lids.
The next day, screw the lids on the jars. Keep homemade cocoa yogurt with stevia refrigerated until ready to use.