Caramelized Onion Puff Pastry Bites with Gruyere and Mushroo

• servings: 30 servings
• total time: 1 hour

Ingredients

4 tablespoons salted butter, divided

2 tablespoons vegetable oil, divided

5-6 ounces crimini or button mushrooms, sliced

2 medium yellow onions, thinly sliced

1/4 teaspoon dried thyme

1 tablespoon sugar

1 1/2 tablespoon balsamic vinegar

1/4 teaspoon garlic powder

salt and pepper, to taste

4 ounces grated gruyere cheese (I used applewood smoked gruyere)

1 package (1 pound) frozen puff pastry, thawed

1 egg, lightly beaten

Directions

MUSHROOMS: In a large cast iron skillet over medium heat, heat 1 tablespoon of oil along with 1 tablespoon of butter. When the butter melts, add the mushrooms and sauté for about 5 minutes until golden and tender. Remove and set aside in a medium bowl.

CARAMELIZE: Heat the remaining 3 tablespoons of butter along with 1 tablespoon of oil and sauté the onions for 5 minutes. Add the dried thyme and sugar and continue to cook for 25 minutes on medium-low heat. Make sure to stir the mixture every 5-10 minutes. If the onions are caramelizing too fast, turn down the heat a little more.

DEGLAZE: Add the balsamic vinegar to deglaze the pan, allow the onions to soak it all in. Turn off heat. Add the onions to the mushroom mixture. Season with the garlic powder and salt and pepper to taste, stir to combine.

MAKE AHEAD: Allow to cool to room temperature. The mixture can be kept in an air-tight container in the fridge for up to 48 hours. Allow to come to room temperature before proceeding. Add the gruyere cheese and mix well.

PREP FOR BAKING: Position two racks in the upper and lower thirds of the oven. Preheat the oven to 400º F. Line 2 baking sheets with parchment paper or silicone mats.

FILL: Using a sharp knife or a pizza cutter, cut the puff pastry into 2-inch squares and place them on a lined baking sheet. Make sure the puff pastry is cold before proceeding. If not, allow it to rest in the refrigerator for 10-15 minutes before proceeding. Using a pastry brush, brush the beaten egg on the squares. Prick the puff pastry using a fork in the center. Place a tablespoon of caramelized onion mixture in the center.

BAKE: for 20-25 minutes, rotating the pan halfway in between until crisp and golden brown. Let cool slightly before serving.