Braised young or baby leeks

SOURCE This recipe is adapted from the BBC Good Food website.
We have changed the recipe slightly and made some of the steps more explicit for the novice cook.
Serves 2 as a side serving
Time (approx): preparation 10m cooking 25m

280g young/baby leeks
c.30g butter
10ml/2 tsp Seven Acres vegetable stock concentrate*
500ml water
handful fresh thyme sprigs, plus extra leaves to serve
* Or 500ml good-quality vegetable or chicken stock.
Knife with a sharp blade
Plastic or wooden spoon or spatula for stirring
Large frying pan
Measuring jug.
A hob or other direct heat source for cooking; Space to prepare the leeks.
Advance preparation
None required.
Preparing the Vegetables
Trim the leaves and end of the leeks, then wash carefully.
Cooking the meal
Heat the butter in the frying pan. Add the leeks, then roll them around to coat them in the butter.
Mix the stock concentrate with 500ml of water and add to the pan.
Bring to the boil, then turn down the heat and add the thyme.
Simmer for 20 mins or until tender.
Serve with a sprinkling of thyme leaves.
Suggested accompaniment
This is an ideal substitute for Brussels sprouts at Christmas (for members of that strange tribe that shuns the sprout!). At other times, it would go well with most meats and other richly flavoured main dishes.