How to Thicken Au Jus Gravy | A Broth to Gravy Roadmap

To thicken au jus into gravy, whisk a slurry of 1 tablespoon cornstarch and 1 tablespoon cold water per cup of simmering liquid.

You pull a beautiful roast from the oven. The pan drippings are fragrant, intensely beefy, and completely thin. That thin jus tastes great, but it slides right off your meat and pools on the plate without clinging to a single bite.

Thickening that au jus into a proper gravy is a simple fix that changes the entire plate. All you need is the right technique and a few minutes. This article covers the three best methods — cornstarch slurry, roux, and reduction — so you can choose the one that fits your meal and your schedule.

Three Ways to Thicken Au Jus

The Cornstarch Slurry Method

Cornstarch is the top choice for au jus. It creates a glossy, translucent finish that keeps the natural color of your drippings intact. Mix equal parts cornstarch and cold water, whisk it into the simmering liquid, and it thickens in under a minute. It is also naturally gluten-free.

The Flour Roux Method

For a more traditional gravy body, a roux works beautifully. Cook equal parts butter and flour together for a few minutes to remove the raw taste, then whisk in your au jus. This creates a matte, opaque finish that pairs well with hearty roasts.

A third option is the reduction method. Simply simmer the au jus until enough water evaporates to thicken it naturally. This relies on concentration alone, so it takes longer and won’t deliver the body of a starch-thickened gravy.

Why Cornstarch Beats Flour for This Job

Au jus is prized for its clear, beefy essence. A flour roux clouds that clarity, which is fine for a brown gravy but not always what you want from a jus. Cornstarch preserves the transparency and adds a professional sheen.

• Glossy, Translucent Finish: Cornstarch thickens without clouding the liquid, keeping the au jus vibrant.
• Powerful Thickening Action: 1 tablespoon of cornstarch has roughly the thickening power of 2 tablespoons of flour.
• Gluten-Free Standard: It is the standard alternative to wheat flour for gluten-free diets.
• Quick Activation: It activates in less than a minute at a simmer, so you can adjust the thickness on the fly.

Flour is not wrong. It has its place in gravies that match heavier dishes like pot roast or stew. For a simple roast beef or prime rib dinner, cornstarch matches the character of the jus better.

Mastering the Cornstarch Slurry for Au Jus Gravy

Making a cornstarch slurry is a straightforward process. The key is mixing the cornstarch with an equal amount of cold water before it ever touches the hot liquid. This prevents lumps from forming.

The standard ratio is 1 tablespoon of cornstarch per cup of liquid. The Kitchn’s guide on cornstarch thickens quickly notes that it usually takes under 60 seconds once the liquid reaches a full simmer. Whisk the slurry in slowly while stirring constantly.

For a thicker, gravy-like consistency, use up to 4 tablespoons of cornstarch mixed with an equal amount of cold water. Start with less and add more as needed, letting each addition come to a full simmer before assessing the texture.

These ratios apply to every cup of liquid you plan to thicken. Scale them up or down depending on how much au jus you have in the pan.

How to Avoid Lumps and Fix a Thin Gravy

Lumps ruin the texture of an otherwise perfect gravy. You can avoid them entirely with these simple steps.

1. Mix a proper slurry. Whisk the cornstarch and cold water together until the mixture is completely smooth with no dry pockets.
2. Whisk constantly. Pour the slurry into the simmering au jus while whisking vigorously. Do not dump it in all at once.
3. Let it simmer. Starch needs heat to activate. Let the gravy come to a full simmer and cook for 30 to 60 seconds.
4. Check and adjust. If it does not thicken enough, whisk in more cornstarch slurry a little at a time, letting each addition come to a simmer before adding more.

Avoid boiling the gravy for too long after adding cornstarch. Extended boiling can break down the starch structure and thin the gravy out again. Turn the heat off once it reaches the consistency you want.

The Exact Cornstarch to Liquid Ratio You Need

Getting the ratio right is the most important part of the process. Start with 1 tablespoon of cornstarch per cup of liquid for a light, silky finish. This produces a jus lié, a lightly thickened sauce that still pours easily.

For a full gravy body, use 2 tablespoons of cornstarch per cup. For a thick gravy that coats the back of a spoon, use 3 to 4 tablespoons per cup. Real Simple’s breakdown of the cornstarch to liquid ratio confirms that cornstarch is twice as powerful as flour by volume, so swapping them blindly will change your results.

Remember that cornstarch thickens more powerfully than flour. Substituting them one for one will give you a much thicker result than expected. Stick to the ratios above and adjust gradually until you hit the right body.

The Bottom Line

Thickening au jus is one of the quickest ways to elevate a roast dinner. The cornstarch slurry method is the best all-around choice for its speed, clarity, and gluten-free fit. The roux and reduction methods are excellent backups depending on the dish you are serving.

These ratios and techniques work for any amount of pan drippings you have in your kitchen. Adjust the thickness to your personal preference, and you will get a flawless, lump-free result every time.