In a pot, heat-up the milk on a low flame.
Right before the boiling point, remove from the heat and let it sit off the flame until it reaches 38° to 40°.
Add the ferment or the yogurt and whisk well. (*At this point, add the sugar and flavoring if desired.).
Fill the multicooker to the first level with water and set the thermostat to 30°.
Line the cups in the perforated Gastro pan (*If you decide to use jam, you can place a couple of tablespoons at the bottom of each cup at this point).
Pour the milk mixture gently in each cup, making sure not to disturb the jam, or create foam.
Cover each cup individually (use little squares of plastic wrap if you don’t have caps).
Place the gastro pan in the multicooker with a lid and let it set for at least 6 hours.
When finished, place the cups in the fridge overnight.
For flavored yogurt (*)