Zwiebelsauce (Viennese Onion Gravy)

Ingredients

Equipment Needed

• •Wide heavy-bottomed pan or skillet (28cm minimum)
• •Wooden spoon
• •Mortar and pestle for crushing caraway seeds

Instructions

1. 1

   Slice the onions

   Halve the onions through the root and slice them into thin half-moons, no thicker than three millimeters. You want a pile that looks absurd, far too many onions for one pan. It isn't. Onions lose about two thirds of their volume as they cook down, and you need that mountain to end up with a proper sauce. Cut them evenly so they caramelize at the same rate. If half your slices are paper-thin and the other half are chunky, some will burn before the rest have even started to color.

   Yellow onions are the standard here. They have the right balance of sugar and bite. Red onions look pretty but turn an odd grayish color in the sauce. White onions don't have enough sweetness to caramelize properly.
2. 2

   Start the slow caramelization

   Melt the clarified butter or Schmalz in a wide, heavy pan over medium heat. A wide pan matters because the onions need surface contact to brown, not crowd together and sweat. Add all the onions, stir once to coat them in the fat, then let them be. After five minutes, stir again. They'll start releasing water and the pan will look like a soupy mess. This is right. Don't panic and don't turn the heat up. Let the moisture cook off slowly. Once the pan goes quiet and the sizzling returns, the onions are ready to start browning.

   Schmalz (rendered pork lard) is the traditional Austrian cooking fat and gives the sauce a rounder, deeper flavor than butter. If you can find it at a butcher or European deli, use it. Clarified butter is the next best thing.
3. 3

   Caramelize deeply

   Now the patience begins. Keep the heat at medium, never higher. Stir every three to four minutes, scraping the fond from the bottom of the pan each time. That dark residue building on the pan floor is concentrated flavor and you're going to dissolve every bit of it into the sauce later. When the onions have been cooking for about twenty minutes total, sprinkle the sugar over them. The sugar doesn't make the sauce sweet. It accelerates the browning and helps the onions reach that deep mahogany color you're after. Keep going until the onions are dark amber and soft enough to crush between your fingers. This takes another ten minutes. The whole process from raw onion to dark caramel should be around thirty minutes. If you get there in fifteen, your heat was too high.

   Gretel always said you can't rush an onion. She was talking about life, but she was also talking about sauce.
4. 4

   Add flour and paprika

   Sprinkle the flour and paprika over the caramelized onions and stir constantly for about one minute. The flour needs to cook in the fat so your sauce doesn't taste starchy. The paprika needs heat to bloom and release its color, but it burns in seconds if your pan is too hot. If you smell anything acrid, pull the pan off the heat immediately. Sweet Hungarian paprika is what you want here. It gives warmth and that deep brick-red color that makes Zwiebelsauce look right.

5. 5

   Deglaze and simmer

   Pour in the warm beef stock in one go and stir, scraping up every bit of fond from the pan. This is where all that patience pays off. Those dark, sticky bits dissolve into the liquid and turn it from pale broth into something with real depth. Add the crushed caraway seeds, bay leaf, and marjoram. Bring to a gentle simmer and let it cook uncovered for fifteen minutes. The sauce will thicken as it reduces and the onions melt further into it. Stir occasionally. You want a gravy that coats the back of a spoon without being gluey.

   Use warm stock, not cold. Cold liquid hitting a hot pan drops the temperature and can seize the flour into lumps before it has a chance to incorporate smoothly.
6. 6

   Finish with vinegar and season

   Remove the bay leaf. Stir in the white wine vinegar. Taste the sauce. It should be savory and rich with a gentle sharpness at the finish that keeps it from being one-note. The vinegar is small but it's doing essential work, cutting through the sweetness of the caramelized onions and the richness of the stock so that every spoonful stays interesting. Season with salt and pepper. The sauce should be thick enough to pool on a plate without running, dark enough to be nearly brown, and full of soft, melting strands of onion throughout. Ladle it generously. Zwiebelsauce is not a drizzle. It's a commitment.

Chef Tips

• •The quality of your beef stock determines the quality of your sauce. If you have homemade stock, use it. If you're using store-bought, look for one with a short ingredient list and real color. If the stock is pale and watery, your sauce will be too. Concentrate it by simmering it down by a third before you start the recipe.
• •Don't stir the onions constantly. They need uninterrupted contact with the hot pan to caramelize. Stir every few minutes, scrape the fond back in, and walk away again. Constant stirring just steams them.
• •This sauce keeps beautifully. Refrigerate for up to five days or freeze for two months. It actually improves overnight as the flavors settle together. Reheat gently with a splash of stock if it's thickened too much in the fridge.
• •For a proper Zwiebelrostbraten, fry thin onion rings separately in clarified butter until crisp and golden, pile them on top of your pan-fried steak, and pour the Zwiebelsauce around, not over. The crispy onion rings and the soft sauce onions together are what make the dish.

Advance Preparation

• •Zwiebelsauce can be made up to five days ahead and refrigerated. The flavor deepens with a day of rest. Reheat slowly over low heat, adding a splash of stock if the consistency has tightened.
• •The sauce freezes well for up to two months. Thaw overnight in the fridge and reheat gently.
• •Slice all onions before you start cooking. Once the pan is hot, you want to work without interruption.

Frequently Asked Questions

Nutrition Information

1 serving (about 125g)