- 1 sheet thawed puff pastry (from a 17.3-ounce package)
- 1 tablespoon extra-virgin olive oil
- 1/4 cup grated extra sharp cheddar
- 3 tablespoons grated Parmesan
- 3 tablespoons chopped fresh herbs (such as thyme, sage, and oregano)
- 1/4 teaspoon coarse salt
- 1 large egg yolk
- 1/2 teaspoon water
Preheat oven to 375 degrees, with racks in upper and lower thirds. On a lightly floured surface, roll out 1 sheet thawed puff pastry to a 10-by-16-inch rectangle. Brush with olive oil and sprinkle with cheddar, Parmesan, herbs, and salt. Fold dough lengthwise into thirds (like a letter), then fold in half. Refrigerate until slightly firm, about 10 minutes. Cut dough crosswise into 1/4-inch-thick slices (you should have about 38).
Place slices on 2 large baking sheets. Refrigerate until firm, about 30 minutes. (To store, cover with plastic wrap and refrigerate, up to 1 day.) In a bowl, combine egg yolk with water. Brush tops of palmiers with egg wash. Bake until golden brown, about 25 minutes, rotating sheets halfway through.