A roux is just butter and flour cooked together, and it’s the secret to a silky, never-grainy cheese sauce for mac and cheese. Learn it once and you’ll never go back to the box. Here’s exactly how I make it, what to watch for, and how to fix it when it goes wrong.

Why this works

• Equal parts butter and flour (3 tablespoons each) make a paste that thickens the liquid without lumps.
• Warm liquid, added a little at a time. Each splash is fully absorbed before the next, so the sauce stays smooth.
• Coconut milk + chicken stock make a creamy sauce that’s lighter than heavy cream.

My tips

• Your liquid should be room temperature or warmed. Cold liquid into a hot roux is how lumps happen.
• Don’t rush: let each addition absorb before adding more.
• The spoon test: the sauce should coat a wooden spoon and stay there. If it runs off, keep cooking. Too thick? Add a splash of stock.
• Add the cheese a handful at a time and let each melt before adding more.

How to fix it

• Lumpy? Whisk hard, or pour it through a strainer. Next time, add the liquid more slowly.
• Too runny? Keep it over the heat a few minutes longer; it thickens as it cooks.
• Grainy cheese sauce? The heat was too high when the cheese went in. Lower the heat first, and shred your own cheese (bagged shredded cheese has coatings that don’t melt as smoothly).

The story behind it

How to Make a Roux and Cheese Sauce

Many people are nervous to make a roux or maybe do not even know what a roux is.  It is quite easy and this post shows you how to make a roux and cheese sauce.  Once you learn how to make a roux, you will never eat macaroni ‘n cheese out of the box again.  We will get to that later.  A roux is a mixture of butter and flour – or should I say a blond roux.  A dark roux is made up of canola oil and flour and is cooked for a much longer period.  A roux is used in many types of cooking –  One as a thickening agent and two as a sauce base.  As you know, using a roux as a thickening agent is a base of Cajun cooking which I used in a number of different ways last week in my Cajun Week: 1)Creole Chili; 2)Cajun Macaroni “n Cheese and 3)Gumbo Pot Pie.

The roux, as noted above, is a mixture of equal parts of butter and flour.  Mixed together well and then a liquid is added to thicken it up. Then, different applications can be developed.  In this case, it is the base for a cheese sauce that I use for macaroni ‘n cheese often.  It is also used for a bechamel sauce (a reader correctly pointed out to me that the correct term for the sauce once the cheese is added is a mornay sauce) commonly used in French cooking as well as in Lasagna for Italian cooking.

Ingredients:

• 3 tbsp butter
• 3 tbsp all-purpose flour
• 1 – 15 oz can of coconut milk
• 6 oz of evaporated milk
• 1/2 cup sharp cheddar cheese
• 1/2 cup of smoked Gruyère

Directions:

Heat a sauté pan on medium high heat.  Add the butter and when melted, add in the flour.

Using a spatula, mix until the flour absorbs all the butter.  The result will be a paste like mixture.

Next, you add your liquid in a little at a time.

The liquid should be room temperature or heated on a low temp if pulled from the fridge.  As you add the liquid to the roux, make sure the initial liquid is fully absorbed before adding in more to your mixture.

Keep adding the liquid until the roux becomes creamy.  If the roux is runny, you have added to much liquid.  Over time, you will learn the consistency you want in your roux.  The roux should look creamy, not runny or to thick.

Once the roux is complete, start adding your cheese a little at a time.

When it is fully melted, add until all the cheese has been used.  Happy cooking and I hope this tip helps you in your cooking.  Enjoy!

Variations

• Cheese swaps: I’ve moved from smoked Gruyère to smoked Gouda. Sharp cheddar plus any smoky cheese works.
• Spice it up: add 2–3 teaspoons of smoked paprika or a pinch of cayenne.
• Gluten-free: a 1:1 gluten-free flour blend can stand in for the all-purpose flour.

Questions people ask

What’s the ratio for a roux?

Equal parts fat and flour by volume: 3 tablespoons butter to 3 tablespoons flour.

How long do you cook a roux for mac and cheese?

Just until the flour absorbs the butter and forms a smooth paste, a minute or two. For a cheese sauce you want it pale, not browned.

Why is my cheese sauce grainy?

Usually too much heat when the cheese goes in, or pre-shredded cheese. Lower the heat and shred your own.

Can I make it ahead?

Yes. Refrigerate the sauce and rewarm it gently with a splash of stock, stirring until smooth.

You might also like: Easy Weeknight Baked Pasta with Fresh Mozzarella · Ultimate Two-Layered Potato Bake · Authentic Mexican Risotto

Made this? Leave a star rating in the recipe card below and tell me how it turned out in the comments. I read every one.

The Recipe

How to Make a Roux and Cheese Sauce

Print Pin

A silky, never-grainy cheese sauce built on a simple butter-and-flour roux. The base for the best stovetop mac and cheese.

Recipe By Feed Your Soul Too

5 from 1 vote

Prep2 minutes mins

Cook12 minutes mins

Total14 minutes mins

Servings6 people

Scale

1x2x3x

Ingredients 

• ▢ 3 tbsp Butter
• ▢ 3 tbsp All-purpose flour
• ▢ 15 Ounces Coconut Milk
• ▢ 6 Ounces Chicken stock, or evaporated milk (my original version)
• ▢ 1/2 Cup Sharp Cheddar, Shredded
• ▢ 1/2 Cup Smoked Gouda, shredded (or smoked Gruyère)

Instructions 

• Heat a sauté pan on medium high heat. Add the butter and when melted, add in the flour. Using a spatula, mix until the flour absorbs all the butter. The result will be a paste like mixture. Next, you add your liquid in a little at a time. The liquid should be room temperature or heated on a low temp if pulled from the fridge. As you add the liquid to the roux, make sure the initial liquid is fully absorbed before adding in more to your mixture. Keep adding the liquid until the roux becomes creamy. If the roux is runny, you have added to much liquid. Over time, you will learn the consistency you want in your roux. The roux should look creamy, not runny or to thick. Once the roux is complete, start adding your cheese a little at a time. When it is fully melted, add until all the cheese has been used. Happy cooking and I hope this tip helps you in your cooking. Serve and Enjoy!

Recipe Notes

I have continued to evolve this recipe.  I now use a little chicken stock in lieu of the evaporated milk.  I also use smoked gouda in lieu smoked gruyere.

Nutrition Information

Calories: 285kcal (14%), Carbohydrates: 5g (2%), Protein: 7g (14%), Fat: 27g (42%), Sodium: 190mg (8%)