Upside-Down Apple-Cheddar Tarts with Frisée and Toasted Walnuts

Ingredients

• Kosher salt and freshly ground black pepper
• 1 Tbs. balsamic vinegar
• ½ cup toasted walnuts, coarsely chopped
• 4 medium Fuji apples
• All-purpose flour as needed for rolling
• 2 Tbs. extra-virgin olive oil
• 2 oz. (4 Tbs.) unsalted butter
• + 3 more ingredients
• • 8 thin slices sharp white Cheddar (about 3 inches square and ¹/₈ inch thick)
  • 1 small head frisée, torn into small pieces (4 cups)
  • 1 9-½ oz. sheet frozen puff pastry, thawed overnight in the refrigerator

Position a rack in the center of the oven and heat the oven to 350°F. On a lightly floured surface, roll out the pastry to a 12x15-inch rectangle. With a 3-1/2- to 4-inch round cookie cutter, cut out 8 disks of puff pastry. Prick each disk all over with a fork. Arrange them on a rimmed baking sh...

View full recipe at Fine Cooking