chop leek and onions into large pieces

dice potatoes into chunks

Chuck everything in slow cooker

cover with stock add salt and pepper to taste.

put slow cooker on low for 5 hours

after 5 hours add creme fraiche, half the pot if you don't.want it too creamy

cook for another 40 minutes

mix cornflour and water together to make a paste, add to soup and stir, then cook for another 20 minutes

serve with crusty bread