Caramelized Onion, Bacon, and Blue Cheese Puff Pastry Tart | Spache the SpatulaEmailFavoritesAddThis

In a large saute pan, heat the butter and olive oil over medium-high heat. Add in the onions and a big pinch of kosher salt, and cook, stirring occasionally, for 25-35 minutes until cooked down and caramelized (you may need to adjust the heat during the cooking process, so they don't burn). Stir the balsamic vinegar into the onions.Preheat oven to 400 degrees, and position the rack in the upper 1/3 of the oven. In a small bowl, combine the sour cream and blue cheese with some salt and pepper.On a lightly-floured work surface, roll the puff pastry out to a 14x10-inch rectangle. Fold 1/2 to 1 inch of the edges in toward the center on all sides. Transfer to large baking sheet.Spread the sour cream and blue cheese mixture into the center of the pastry, and to the edges. Add the caramelized onions evenly over the top, followed by the bacon.Bake for 25-35 minutes until the pastry is golden and cooked, and the toppings are bubbly. Allow to cool slightly, and cut into 12 pieces.