How to make a roux-based sauce

This is one of several "technique" hubs that are spin-offs for a blog article I wrote entitled Learn to Cook: You Know You Want to, but Where do You Start?.

To an inexperienced cook, the very phrase "roux sauce" sounds intimidating - the sort of thing that only French chefs with at least one Michelin star are capable of. That's far from being the truth; making a roux is actually quite simple and once you've mastered it, you'll be able to cook things like lasagna, moussaka or even just a white sauce to go with fish such as cod. You'll also be able to stop buying all those packet sauce mixes. As long as you have flour, butter and milk (and cooking oil will do the job instead of butter), you're all set.

As with a lot of my cooking, I go by guesstimation rather than using exactly measured quantities. The instructions below will make enough sauce to use in a lasagna to serve 2-4 people. What you're aiming for is something the consistency of double cream, without any curdling or lumps. And even if you do get curdling/lumps, you can easily rescue matters with a hand-held blender.

Gently melt about an ounce (25 g) of butter in a saucepan. Before it starts to go brown, add a heaped tablespoon of flour and mix well with butter using a spatula, while the saucepan is still on the heat. What should happen is that you get a golden-coloured, bubbly paste that is quite thick, but still has "flow" to it. If it congeals into a lump (or several lumps) it means you've got too much flour in there. But all you need to do in that case is add a bit of extra butter, so it's no big deal. Stir your "paste" for about 30 seconds but don't let it go brown; when it just starts to do so, take the pan off the heat. Add a tablespoon or so of cold water, and mix well in using your spatula. The paste will lighten in colour and change consistency, into something more akin to wallpaper paste. Add another tablespoon of water, again with vigorous stirring. Then add a tiny bit of milk, again with (you've guessed it) more stirring. Now you can put the pan back on the heat. Add milk, a very little at a time, stirring all the while so that the mixture gradually heats up. It's a sudden change in temperature - combined with insufficient stirring - that causes lumps to form. But as I said, lumps aren't the end of the world - just blitz them with the hand held blender thingy and you'll be fine. And even if you do get a few lumps forming at first, you'll often find that most of them disappear.

It's up to you how much milk you add - with the quantities of butter and flour I've indicated, I would say about half a pint (a quarter of a litre) is right. If you're adding cheese (see below), just grate a couple of ounces (worth doing this before you make the sauce), and add it when you've stirred in the last bit of milk and the sauce has thickened as much as it's going to. Stir well in until the cheese has melted. You may find that the cheese thickens the sauce even more, but you can always add a tiny bit of extra milk to counteract this. If you're wondering what sort of cheese to use, Cheddar is good. Particularly mature cheddar - it has more flavour!

If you're planning to make lasagna but don't know how, read on. Cook the pasta sheets according to the instructions on the packet. In a rectangular Pyrex or metal dish, place a layer of bolognaise sauce, a layer of pasta, another layer of bolognaise sauce (see my blog article on making tomato sauce for how to do this), and another layer of pasta. Add your cheese sauce - it should cover the pasta to a depth of about half an inch or just under. Then add a layer of grated cheese and maybe a light sprinkling of breadcrumbs to impart a bit of crispiness. Cook in a medium oven until the cheese sauce layer starts to go golden brown and bubbly.

A final word on the pasta used to make lasagna: some types of dried lasagna can supposedly be used without cooking them in boiling water first. I find that you get better results if you do boil them, even if it's just for a couple of minutes to soften them up. Otherwise they can come out rather dry and chewy.

© Empress Felicity October 2009