Step 1

Sauté: Heat the butter in a deep and wide skillet over medium heat. Add the onion, garlic and mushrooms and cook until they're soft and lightly browned, about 5-10 minutes.

Step 2

Season: Stir thyme, salt and pepper into mushrooms. Sprinkle pan with flour and stir in well. Stir in tomato paste and cook for 30 seconds, stirring constantly.

Step 3

Deglaze the pan: Increase the heat to medium-high. Wait until pan sizzles, then pour the wine or extra stock over the mushrooms, scratching the browned bits off the bottom of the pan. Reduce the heat to medium-high and cook until almost all of the wine has evaporated.

Step 4

Cook the sauce: Stir in the stock. Simmer the sauce until it has reduced by half. If sauce doesn't thicken/you want a thicker gravy, stir in a slurry of cornstarch and water.

Step 5

Finish: Take the sauce off the heat and stir in the cream, if using.