Extra time:6hr setting ›
- Place four 300ml jars in a slow cooker (I used a 3.5 L slow cooker and four jam jars). Fill with water so that the jars are immersed up to 1cm of their rims. Remove jars and set aside.
- Cover slow cooker with lid and set to High while you prepare the yogurt, about 20 minutes.
- Meanwhile, pour the milk and milk powder into a saucepan. Whisk to dissolve the powder and set over medium heat. Heat until just steaming, about 10 minutes; your thermometer should read 82 degrees C. Remove from the heat and place the pan so the bottom is sitting in a bowl of ice water. Cool until the temperature has dropped to 46 degrees C.
- When it reaches the temperature, remove it from the ice bath and stir about 1 cup of the milk into the plain yogurt until thoroughly blended. Stir this mixture back into the pan of milk. Pour the milk mixture into the four glass jars to within 1-1.5cm of the rims.
- Using your thermometer, check the temperature of the water in the slow cooker. It should be no higher than 46 degrees C. If cooler, cover and allow to come to temperature. If too hot, uncover and turn off slow cooker. (I find the water is typically at the correct temperature at this point, but slow cookers vary.)
- Set jars in the warm water bath. The water level should be up to the level of the yogurt in the jars. Cover with a folded tea towel and then with the slow cooker lid, then shut slow cooker off. Allow to set for 6 hours, keeping the water at 46 degrees C as best you can. Check the temperature with your thermometer after about 2 hours, taking care not to disturb the yogurt. If the water is lower than 46 degrees C, turn slow cooker to Warm for 10 minutes, then shut off. Ideally, check again at the 4 hour mark and repeat. The yogurt should be set after 6 hours. Note: Do not stir or poke the yogurt at all during this time!
- After 6 hours, you can check the yogurt by pressing gently on the top or tipping the jars to see if it is set. It is done when the yogurt is firm and there is a thin layer of yellowish liquid on the top. Remove the jars from the water and dry off. Top with clean lids and place in fridge. They should be good to keep in the fridge for up to 2 weeks.
Be sure to save a little yogurt as a starter for the next batch. Over time your homemade yogurt will start to lose its potency as starter, so every fourth or fifth batch you may need to use shop-bought yogurt as starter.
You can skip the milk powder, but your yogurt won't be as thick. Likewise, you can increase or decrease the amount of milk powder used to achieve thicker or thinner results.
For a super-thick, Greek-style yogurt, simply strain your yogurt after it has set. You can place muslin or a coffee filter in a fine sieve, then add the yogurt and set it over a bowl to catch the liquid. Strain overnight in the fridge.