- Butter for greasing baking sheet
- 1 frozen puff pastry sheet (from a 17 1/4-oz package), thawed
- 1 egg white, lightly beaten
- 27 pitted prunes (sometimes called dried plums; 1/2 lb)
- 1 tablespoon sugar
- 1/4 teaspoon cinnamon
- Put oven rack in upper third of oven and preheat oven to 425°F. Butter a baking sheet.
- Unfold pastry sheet and cut into 9 (3-inch) squares, then arrange squares on baking sheet. Lightly brush squares with some of egg white. Toss prunes in remaining egg white. Arrange 3 prunes in center of each square, letting excess egg drip off and leaving about a 1/2-inch border around edge. Stir together sugar and cinnamon and sprinkle over tartlets.
- Bake until pastry is puffed and golden brown, 10 to 15 minutes. Transfer tartlets to a rack and cool to warm, about 10 minutes.