Savory Mushroom Onion Tart (Printable View)
Flaky tart with caramelized onions, mushrooms, and creamy cheese for a tasty vegetarian dish.
# Ingredient List:
→ Pastry
01 - 1 sheet ready-made puff pastry, thawed (approx. 8.8 oz)
→ Vegetables
02 - 2 tablespoons olive oil
03 - 1 tablespoon unsalted butter
04 - 2 large yellow onions, thinly sliced
05 - 14 oz cremini or button mushrooms, sliced
06 - 2 cloves garlic, minced
→ Filling
07 - 3 large eggs
08 - 2/3 cup heavy cream
09 - 1 cup grated Gruyère or Swiss cheese
10 - 1 tablespoon fresh thyme leaves (or 1 teaspoon dried)
11 - 1 teaspoon salt
12 - 1/2 teaspoon ground black pepper
→ Garnish (optional)
13 - Fresh chives or parsley, chopped
# How to Make It:
01 - Preheat oven to 400°F. Line a 9-inch tart pan with parchment paper.
02 - Roll out puff pastry and press into the tart pan. Trim excess and prick base with a fork. Chill while preparing filling.
03 - Heat olive oil and butter in a skillet over medium heat. Cook onions, stirring, until soft and golden, about 12 minutes.
04 - Add mushrooms to the skillet and cook 8 to 10 minutes until they release moisture and turn golden. Stir in garlic and thyme; cook 1 minute more. Remove from heat and cool slightly.
05 - Whisk eggs, heavy cream, salt, and pepper in a bowl. Fold in grated cheese.
06 - Spread onion and mushroom mixture evenly over chilled pastry shell. Pour egg and cheese mixture on top.
07 - Bake for 25 to 30 minutes until filling is set and pastry is golden brown.
08 - Allow tart to cool for 10 minutes. Garnish with fresh herbs if desired, slice, and serve warm or at room temperature.
# Expert Suggestions:
01 -
- The caramelized onions taste like pure comfort—sweet, deep, and almost like they've been cooking for hours when they've really only taken twenty minutes of gentle attention.
- It works equally well as a fancy dinner centerpiece or a casual lunch with a green salad, which means you can make it confident it'll fit whatever mood strikes.
- Once you've made it once, you'll realize you can swap in whatever cheese or herb you have on hand, which means it never feels like the same tart twice.
02 -
- Don't skip the chilling step for either the pastry or the vegetable cooling—both prevent the crust from shrinking and the eggs from scrambling, which are the two most common things that go wrong.
- Caramelization is a waiting game, and rushing those onions by turning up the heat will give you brown onions rather than caramelized ones, which taste completely different—low and slow is the only way.
- A slight jiggle in the very center of the custard when you pull it from the oven is perfect; a completely firm tart has been overbaked and will be drier than it should be.
03 -
- A splash of white wine added to the mushrooms as they finish cooking adds a subtle depth and helps their flavor develop even further—you'll taste something richer that's hard to pinpoint, and that's the wine doing its magic.
- Make this tart a day ahead, refrigerate it, and reheat gently in a low oven for fifteen minutes just before serving—the flavors somehow taste even better the next day, and it takes stress out of entertaining.