How to make a roux

A roux (pronounced “roo”) is simply a mixture of fat and flour cooked together, used for thickening sauces. It’s an essential element in many recipes and one of the most fundamental cooking techniques. Butter is the most common ingredient for the fat element, but oil or lard can also be used. A roux is typically made with an equal ratio of fat to butter based on weight – for example, 50g of flour and 50g of butter. After a roux is made, it's incorporated into sauces by slowly adding a liquid like milk or stock until the mixture is dissolved. The result is a rich, silky sauce which would otherwise be too runny or thin without using a roux as a base.

Step 1. Melt butter

Melt 50g of butter, or whatever fat you’re using, slowly in a saucepan over medium heat-low heat. Make sure to keep an eye on the butter to make sure it doesn’t brown or burn.

Step 2. Add flour

Once the butter is melted, slowly whisk in 50g of flour and gently mix to incorporate. Don’t use a metal whisk if you’re using a non-stick pan as this may scratch the surface and damage the non-stick coating.

Step 3. Cook the flour

Allow the flour to cook off in the fat on a medium-low heat. It should bubble gently as it forms a thick paste. Keep stirring the mixture and don’t allow it to bubble too much as it may burn if the heat is too high. Cook for three to five minutes for a white roux.

Create your sauce by slowing pouring in milk or stock and whisk vigorously to make sure the roux is evenly distributed. Leave to simmer for a few minutes.

There are a few pitfalls when learning how to make a roux that you may fall into. We asked our resident food expert – M&S Food Editor, Florence Bischoff – for some expert tips.

"If you have the patience, it's best to cook your roux low and slow, especially if you're nervous about burning it. A little brown butter never hurt anyone so not all is lost if you start to smell those toasty aromas. However, if you start to see little black flecks in your roux, it's likely game over. Wipe your pan clean and start again," Florence explains.

She also has some great advice for avoiding any lumps in your roux. "Lower the heat, work slowly and just keep whisking. I will often have a spatula on hand as well as a whisk, to get those pesky bits of flour that stick to the sides of the pan and alternate between the two as you work. If it's lumpy and you feel like there's no turning back, let it cool slightly and blend until silky smooth and then return to continue to cook out the flour as needed."

Our easy roux recipe will make cooking sauces, stews and gravies a dream. Although on those busy weeknight you may want to take some shortcuts to whip up dinner in a flash. Keep a jar of our gently seasoned Classic Béchamel Everything Sauce in the cupboard to use in everything from fish pie to pasta. Whipping up a mac and cheese? Our decadent Four Cheese Sauce is made from a blend of British and Italian cheeses including Grana Padano, provolone, Pecorino and mascarpone. Our extensive Foodhall has a great selection of sauces, condiments and dressings for every occasion.