To make the Egg en Cocotte
Pre-heat the oven to 180C and put a kettle on to boil.
Gently saute the leeks with the tsp butter and a little salt and pepper, then let them begin to steam in own juices in a small pan with a lid for 5 minutes.
Divide the cooked leek between the ramekins and place them in the roasting tin then break an egg into each ramekin, add some more seasoning, then put a tablespoon of crème fraîche on top of each yolk. Put a couple of sprigs of fresh dill on top.
Place the roasting tin on the centre shelf of the oven and pour enough hot water, from the kettle, into the tin to come halfway up the sides of the dishes. Now let the eggs bake for 15 minutes if you like them soft and runny, or 18 minutes if you like them more set.
Top with a tsp fish eggs and serve with a slice of toasted sourdough or rye toast.