Heat oven to 200C/fan180C/gas 6. Cook the leeks in a pan of boiling salted water for 5-6 mins until tender. Drain leeks thoroughly and allow to cool, pat dry with kitchen roll to ensure excess liquid removed
Wrap a slice of ham around each leek and place seam down in a shallow baking dish
Place crème fraiche in mixing bowl and mix in Worcester sauce, mustard and seasoning. Add 100g of cheddar and mix thoroughly.
Spoon over the leeks, sprinkle over remaining cheddar and bake for 20 mins until golden and bubbling.
Serve immediately with plenty of crusty bread to soak up sauce and a crisp green salad
(For vegetarian version omit ham and replace with red peppers from a jar.)