Finely chop the mushrooms until they are almost minced. This is crucial. Hardee’s mushroom sauce doesn’t have chunky mushroom pieces — the texture is smooth and cohesive.

Pro tip: A food processor works great, but don’t puree them. Pulse until finely chopped.

In a skillet, heat the olive oil and butter over medium heat.

Add the mushrooms and spread them out evenly.

Cook for 6–8 minutes, stirring occasionally. The mushrooms will release moisture first — let it evaporate fully. Continue cooking until the mushrooms begin to brown and stick slightly to the pan.

This browning step is where the deep umami flavor develops. Do not rush it.

Once mushrooms are browned:

Add minced onion

Cook for 2 minutes, stirring constantly

Cook the garlic for 30 seconds until it becomes fragrant.

The onion should soften and lightly caramelize, adding subtle sweetness.

Pour in beef broth and Worcestershire sauce.

Scrape the bottom of the pan to release all those flavorful browned bits.

Let the mixture simmer for 2–3 minutes until slightly reduced.

At this stage, the sauce will be loose but extremely aromatic.

In a small bowl, mix cornstarch with cold water to form a slurry.

Slowly stir it into the pan.

Cook for 1 minute, stirring continuously, until the sauce thickens slightly and becomes glossy.

This is a light thickening, not a gravy. The sauce should easily spoon over a burger.

Season with black pepper and salt to taste.

If using cream, add 1–2 tablespoons and stir gently.

Remove from heat immediately once the desired texture is achieved.