Place the can (or cans) into the slow cooker and cover with hot (but not boiling) water.Ensure the water is 5cm above the top of the can. Note: if using a ring pull can, make sure the ring pull is facing downwards.
Cook on LOW for 8 hours (up to 10 hours for a thicker caramel).
Very carefully remove the can from the slow cooker and place into a bowl of cold water to cool (approximately 15 minutes). Alternatively you can switch off the slow cooker and leave it overnight to cool.
Open the can when cooled and serve with your favourite dessert.
Notes
RECIPE NOTES AND TIPS
Make sure to use full fat condensed milk, not skim.
Double the recipe by cooking two cans at a time.
There's no need to remove the labels prior to submerging in the water. They will lift off on their own during cooking.
Check the water level stays 5cm above the can at all times during cooking (some slow cookers release more liquid/steam than others and may need topping up). If the water level goes below the top of the can, it may burst (very dangerous!). I recommend checking the water level every hour.
Store any leftover caramel in an airtight container in the fridge for up to 3 weeks.