Leek and Celeriac Gratin - An adaptable gratin of leek and celeriac that can be used as part of the 5:2 fast diet or can be enjoyed on non-fast days by adding extra cream and cheese
Spray an ovenproof skillet with 1cal or (for the full-calorie version) melt 25 g of butter.
Gently sweat the leeks and garlic for about 10 minutes till soft.
Pour over the milk and bring to the boil. Season well with salt and pepper and put to one side.
Put a spoonful of the leek and milk mixture onto the bottom of the skillet and spread around.
Top with a layer of celeriac on the bottom of the casserole, then leeks, then celeriac until everything is used. Season each layer with a little salt and pepper.
If you are using cheddar cheese, top each celeriac layer with some of the cheese. Reserve 25g of cheddar
Pour over any remaining milk mixture, together with the cream if you are using it.
Top everything with the finely grated parmesan and the optional cheddar. Put in the oven at 170c for 60 minutes until the celeriac slices are tender and the top is golden