Vegetarian · Tested twice

Caramelized Onion Mushroom Galette

Name: Caramelized Onion Mushroom Galette
Prep time: 30 min
Cook time: 50 min
Total time: 80 min
Yield: 6 servings
Cuisine: American
Ingredients: 1 1/4 cups all-purpose flour; 1/2 teaspoon salt; 9 tablespoons cold butter, cubed; 3 to 4 tablespoons ice water; 3 large onions, thinly sliced; 2 tablespoons olive oil; 1 tablespoon sherry or cider vinegar; 12 oz mushrooms, sliced; 2 cloves garlic, minced; 1 teaspoon fresh thyme leaves; 3 oz Gruyère, grated; 1 egg, beaten, for the crust; Flaky salt and black pepper

The onions need forty minutes and cannot be hurried, which is the entire recipe. Everything else takes twenty and the oven does it.

30 minPrep

50 minCook

1 hr 20 minTotal

6Serves

How it balances

Where this dish sits as written, and what each dial is doing.

SaltSalted pastry, salted onions, Gruyère

AcidOnly a splash of vinegar in the onions

FatButter pastry and cheese — the dominant dial

HeatNone, by design

Method

Rub the cold butter into the flour and salt until the mixture holds large, uneven pieces. Add the ice water a tablespoon at a time until it just comes together, then flatten into a disc and chill 30 minutes.
Cook the onions in the olive oil over medium-low heat for 35 to 40 minutes, stirring occasionally, until deep golden and jammy. This cannot be rushed at higher heat — they will scorch at the edges and stay raw in the middle.
Deglaze with the vinegar, scraping the pan, and set aside.
In a separate pan over medium-high, brown the mushrooms 6 to 8 minutes without crowding, then add the garlic and thyme for 1 minute. Season.
Roll the pastry into a rough 12-inch circle on parchment. Scatter the Gruyère over, leaving a 2-inch border, then the onions, then the mushrooms.
Fold the border over the filling in loose pleats, brush with egg, and bake at 400 degrees F for 35 to 40 minutes until deeply golden. Cool 10 minutes before cutting — warm, not hot, is when it tastes best.

If it tastes flat

Acid, easily. This is a rich, sweet, buttery dish with almost no brightness in it, so it goes flat before it goes under-seasoned. Deglaze the onions with a tablespoon of sherry or cider vinegar, and serve a sharply dressed green salad alongside rather than adding salt.

The bit that matters

Give the onions the full forty minutes. Every shortcut version of this dish fails in the same place: onions cooked hot and fast taste sharp and thin, while onions cooked slowly turn sweet enough to carry a tart with almost nothing else in it.

*Approximately 480 calories per serving. Calories are an estimate from standard ingredient databases; actual values vary by brand and portion. See our disclaimer.