Step 1: Heat the milk. Pour the milk into a saucepan, clip the thermometer onto the side, turn the heat to medium and leave it for 20 minutes until it reaches 85°C/185°F. I like to set a timer so that I don't forget about it.
Step 2: Cool the milk. Take the pot off the element and leave it sitting for 40 minutes until it reaches 45°C/113°F. I also use my kitchen timer here.
Step 3: Mix in the yoghurt. Once the milk has cooled to the right temperature, add the yoghurt to the jar you will be using and pour in 1 cup of the milk. Stir it up and then add the remaining milk and stir again.
Step 4: Incubate. Now the yoghurt needs to be incubated so that it can turn into yoghurt! It usually takes around 4-5 hours to set but the longer you leave it, the thicker and tangier the yoghurt. I like leaving mine for around 8 hours, but you can play around with it! At this stage you have a few options depending on which method you want to use to incubate the yoghurt.
Method 1: Yoghurt maker - if you have a yoghurt maker, this is the easiest option. Pour boiling water into the bottom of the yoghurt maker (I pour in enough so that the water isn't touching the jar.) Leave on the bench for 6-10 hours. Method 2: The oven - heat the oven to the lowest temperature (it's 50°C/122°F on my oven) then turn off the oven but leave the oven light on and place the yoghurt jar in the oven. Leave for 6-10 hours. Method 3: Slow cooker - I've tried a couple of different ways with the slow cooker. The only thing to note with the slow cooker is that you may need to make your yoghurt in two smaller jars. If I'm making it in the slow cooker I use 500ml Agee jars. You can half fill the slow cooker with warm water, place the yoghurt jar in it, wrap the whole slow cooker in a towel and leave for 6-10 hours. The other way I did it was pouring hot tap water into the slow cooker, turning it to warm and leaving the yoghurt in there for 6 hours. I didn't like this method as much as wrapping it in a towel and leaving it for longer.
Step 5: Refrigerate. Once the yoghurt has set, it needs to be refrigerated. Place in the fridge overnight or until cooled completely. At this stage you can also stir in any flavours you like or strain it to make thicker Greek yoghurt.
Yoghurt will store in the fridge for up to 2 weeks and you can now use the last of this homemade yoghurt to make your next batch! I made my first batch of yoghurt in March and have been using my own yoghurt to make new batches ever since!