Leek and Cheddar Welsh rarebit

A simple but logical twist on a traditional rarebit. Brown sauce is not essential, but does make a nice addition .
You can make extra cheese sauce for another day; it’s great added to cooked and sliced jacket potatoes and heated in the oven.

50g unsalted butter
200g (about 3 medium) leeks, roughly chopped and well washed
50g plain flour
200ml whole milk
120g mature Cheddar, grated
2 egg yolks
sea salt and freshly ground black pepper
4 slices of thick wholemeal bread
Put the butter in a saucepan set over a low heat, melt, then add the leeks and gently sweat until very soft. Add the flour and stir, cooking for 1 minute. Now gradually add the milk and bring to a simmer for 1 minute. Allow to cool a little, then fold in the cheese, then the yolks, and season.
Meanwhile, grill the bread on one side, turn over and spread generously with the cheese sauce. Place back under the grill and cook until the cheese is golden and bubbling.
Serve with brown sauce.