Here’s a clear, step‑by‑step guide to how to make a roux for mac and cheese, plus some pro tips so your sauce turns out silky instead of grainy.

What a roux is (and why it matters)

A roux is just equal parts fat (usually butter) and flour, cooked together, then thinned with milk or cream to make a béchamel, which becomes your cheese sauce. For mac and cheese, you want a pale, lightly cooked roux so the sauce is creamy and smooth, not dark or nutty like for gumbo.

Basic formula for mac and cheese

For most stovetop mac and cheese:

  • 2 tablespoons butter
  • 2 tablespoons all‑purpose flour
  • About 2 cups milk (whole milk or 2%)
  • 1½–2 cups shredded cheese (cheddar or a mix)

This makes enough sauce for roughly 8 ounces (about 2 cups dry) pasta, depending on how saucy you like it.

You can scale the roux like this per 1 cup of liquid:

  • Thin sauce: 1 tbsp butter + 1 tbsp flour
  • Medium sauce (good for mac): 2 tbsp butter + 2 tbsp flour
  • Thick sauce: 3 tbsp butter + 3 tbsp flour

Step‑by‑step: making the roux

1. Melt the butter

  1. Put a medium saucepan or pot over medium heat.
  2. Add the butter and let it fully melt; it may foam a little as water evaporates.

You want the butter melted and just starting to foam, not browned.

2. Add the flour

  1. Sprinkle in the flour gradually , whisking constantly to form a smooth paste.
  1. Scrape the corners of the pot so no dry flour hides there.
  2. The mixture should look like a thick, smooth paste and gently bubble.

If it looks very dry and crumbly, you can add a tiny bit more butter; if it’s oily and loose, add a pinch more flour.

3. Cook the roux

  • Keep the heat at medium to medium‑low.
  • Whisk continuously for about 2–3 minutes until the roux turns a pale golden color.
  • You should no longer smell raw flour; instead it should smell slightly toasty.

For mac and cheese, stop at this light stage; darker roux has more flavor but less thickening power and will give you a browner sauce.

Turning the roux into cheese sauce

4. Add the milk (turning it into béchamel)

  1. Warm the milk slightly (microwave 30–60 seconds) so it’s not fridge‑cold; this helps avoid lumps.
  1. With the pan still over medium heat, slowly pour in a splash of milk , whisking vigorously.
  2. Once that first bit is smooth, add more milk, a little at a time, whisking constantly.
  1. As it loosens, you can add the rest of the milk in a thin stream while whisking.

Keep cooking and whisking until the sauce gently bubbles and thickens enough to coat the back of a spoon, usually 3–5 minutes.

At this point you have a basic béchamel sauce , the classic base for mac and cheese.

5. Season and add cheese

  1. Turn the heat to low.
  2. Season the béchamel lightly with:
    • Salt and pepper
    • A pinch of dry mustard, paprika, garlic powder, or onion powder if you like.
  1. Add shredded cheese by the handful , whisking between additions until fully melted and smooth.

Avoid very high heat here; cheese can split or turn grainy if boiled hard.

Texture, timing, and troubleshooting

How to know your roux is right

  • Looks: Smooth paste, pale yellow, not dark brown.
  • Smell: Mildly toasty, not raw flour.
  • Feel: Gently bubbling, not frying hard in oil.

If it’s browning quickly, turn the heat down and lift the pan off the burner for a moment while whisking.

Avoiding lumps

  • Use warm (not cold) milk and add it gradually while whisking non‑stop.
  • If lumps form, whisk vigorously off the heat; in stubborn cases, you can strain the sauce before adding cheese.

Avoiding grainy or greasy cheese sauce

  • Use cheese you grate yourself; pre‑shredded often has anti‑caking starches that can make sauce gritty.
  • Keep heat low once cheese goes in and don’t boil after adding cheese.
  • If it looks greasy, you may have added too much cheese or used very high heat; whisk in a splash of warm milk to bring it back together.

Simple example recipe (putting it all together)

  1. Cook 8 oz elbow macaroni in salted water; drain.
  2. In a pot, melt 2 tbsp butter over medium heat.
  3. Whisk in 2 tbsp flour; cook 2–3 minutes until pale golden.
  4. Slowly whisk in about 2 cups warm milk; simmer and whisk until thickened, 3–5 minutes.
  1. Season with ½ tsp salt, ¼ tsp pepper, pinch of paprika or dry mustard (optional).
  2. Reduce heat to low; add 1½–2 cups shredded sharp cheddar in handfuls, stirring until smooth.
  1. Stir in the cooked pasta and serve right away, or transfer to a baking dish, top with a little extra cheese or breadcrumbs, and bake until bubbly.

Mini “Quick Scoop” recap

  • Equal parts butter and flour = your mac and cheese roux.
  • Cook 2–3 minutes over medium heat until lightly golden to remove raw flour taste.
  • Slowly whisk in warm milk to make a smooth béchamel, then melt in cheese on low heat for a creamy sauce.

Information gathered from public forums or data available on the internet and portrayed here.