“A stew without an onion is worse’n a matinee without candy,” laments Hetty, the protagonist who obsesses over the allium deficiency in her meat-and-potatoes boil. Without it, she says, “it ain’t got any soul.”
Truer words have never been said about what onions can do for a sauce—especially when it’s the gravy poured over bangers and mash. Rich in color, body, and savoriness, onion gravy is what merges the plump sausages and buttery spuds into the cozy British pub staple that this dish is.
If you’ve ever caramelized onions, you know it takes a bit of coaxing for them to go from sharp and crunchy to silky and sweet‑savory, so I slice them thin for maximum heat exposure and add them to the skillet as soon as the fresh, lightly spiced Cumberland links (the traditional choice, though bratwurst also works well) start to brown. Then I drizzle in some water and cover the pan, harnessing steam power to gently cook the sausages and wilt the onions. Once the links are cooked through, I set them aside while the onions keep going. Eventually, the water evaporates and the onions caramelize, building up a deep, dark, meaty fond on the bottom of the pan.
Sign up for the Cook's Insider newsletter
The latest recipes, tips, and tricks, plus behind-the-scenes stories from the Cook's Illustrated team.
The Evolution of Great Gravy
STEAM the onions with the sausages to help them collapse.
SAUTÉ them until well browned and a meaty fond forms in the pan.
SIMMER them in seasoned beef broth until the gravy has reduced.
To capture every bit of that savory flavor base, I deglaze the pan with beef broth that I season with dry mustard; rosemary; thyme; and Marmite, the glutamate-rich British yeast extract that infuses the gravy with meaty, fussed‑over flavor. A brief cook softens the onions and concentrates the gravy even more.
Finally, to achieve the requisite body and gloss, I add a cornstarch slurry and a few knobs of butter, whisked in off the heat. I brighten the sauce with vinegar and spoon it over the links and mash. Savory? Check. Cozy? Check. Soul-satisfying? You bet.