Let me start by saying these tarts are insanely good. I dare you to try and eat just one, you can't trust me. These would be great to serve at a party but I ended up making them for lunch when I had my friend Katie over. I served the tarts with a Citrus Kale Salad and it was in my humble opinion the perfect lunch- well perhaps a glass of chilled white wine would have made it better.
You can cut the tarts as big or as small as you like. I used my second largest biscuit cutter which is approx 3 inches wide. I thought the tarts were the perfect size not too small or big. I see these tarts being made very often in my future! You could honestly do any toppings but the mushrooms, onions, and Gruyere pair together perfectly. These little tarts are melt in your mouth good!
Caramelized Onion, Mushroom & Gruyere Tartlets
1 tablespoon olive oil
1 large yellow onion, thinly sliced
1 tablespoon unsalted butter
16 ounces white button mushrooms, thinly sliced
1 clove garlic, chopped
½ teaspoon dried thyme
Salt and pepper, to taste
¼ cup white wine (can substitute chicken or vegetable broth)
2 sheets puff pastry (thawed according to directions on package)
1 cup shredded Gruyere cheese (can substitute any variety of Swiss cheese)
1/4 Cup Parmesan Cheese (I like mine cheesy so I added this cheese on top)
1 egg + 1 tablespoon water, beaten together (for the egg wash)
Handful of parsley, chopped
1. Preheat oven to 400 degrees F and line two baking sheets with parchment paper.
2. Heat the olive oil in a wide, heavy-bottomed pan over medium-low heat and add the onions. Cook, stirring occasionally, until they begin to caramelize, about 20 minutes.
3. Add the butter to the pan. Once melted, add the mushrooms and saute, stirring occasionally, until they are completely soft and all of the liquid evaporates, about 20 minutes.
4. Add the garlic and the thyme and saute until fragrant, about 1 minute. Season with salt and pepper to taste.
5. Add the wine, scraping the bottom of the pan to pull up all of the browned bits, and cook until all of the liquid has evaporated. Remove from heat.
6. Unfold the thawed sheets of puff pastry and cut out circles from the dough, placing them evenly spaced on the baking sheets. Using a very sharp knife, make four small scores around the perimeter of the dough, about ¼ to ½-inch from the edge.
7. Top the rounds of puff pastry with a small spoonful of the onion and mushroom mixture, trying to keep the filling within the score marks. Top with the shredded Gruyere cheese. Brush the edges of the dough rounds with the egg wash.
8. Bake until the pastry is golden brown, about 15 to 25 minutes. Garnish with fresh chopped parsley.
Recipe and top photo adapted from The Brown Eyed Baker