Ingredients
2 tbsp. extra-virgin olive oil
1 tbsp. unsalted butter
4 medium yellow onions, thinly sliced
Kosher salt
Freshly ground black pepper
1 tbsp. balsamic vinegar
1 tbsp. fresh thyme leaves, plus more for serving
All-purpose flour, for surface
2 sheets frozen puff pastry (from a 17.3-oz. package), thawed in refrigerator
1 large egg, beaten to blend
4 oz. goat cheese, crumbled
2 tsp. honey
Preparation
Step 1In a large skillet over medium heat, heat oil and butter. Add onions, 2 teaspoons salt, and 1/4 teaspoon pepper and cook, stirring occasionally, until very onions are very caramelized, about 35 minutes. Stir in vinegar and thyme. Let cool to room temperature.Step 2Arrange racks in upper and lower thirds of oven; preheat to 375°. Line 2 baking sheets with parchment.Step 3On a lightly floured surface, cut each puff pastry sheet into 9 (3"-by-3") squares. Transfer squares to prepared sheets. Top each with about 1 tablespoon onions, leaving a 1/2" border on all sides. Brush exposed edges with egg. Divide goat cheese among squares. Step 4Bake tarts, rotating sheets front to back halfway through, until puffed and golden brown, 25 to 28 minutes. Drizzle a little honey on each tart. Top with more thyme and pepper. Serve immediately or at room temperature.
Remember to leave enough time for your puff pastry to thaw before you start—it takes about 4 hours in the refrigerator. Caramelizing onions takes a bit of time and a watchful eye, but the deep onion-y flavor is well worth it. If your onions start to burn or stick to the pan, simply add a tablespoon or two of water to loosen them and slow down the cooking. The water will evaporate, leaving behind perfectly caramelized onions. A tablespoon of balsamic vinegar, stirred in at the end, balances the deep umami flavor of the onions with a hit of acid. Once the onions are cooled to room temperature, you’ll scoop a bit of them onto each puff pastry square with a little crumbled goat cheese for creaminess and tang. The final step is a light drizzle of honey for that salty sweet combination everyone loves. It’s a good time to bust out a good-quality honey that you’ve been saving. Made this? Let us know how it went in the comments below!