Heat oven to 400°F. Line 2 baking sheets with nonstick foil, or with regular foil coated with nonstick cooking spray.
Unfold pastry sheets on work surface. Slice sheets along the fold lines, making six pieces, 10 inches by about 3 inches. Cut 4 of the strips crosswise into thirds, creating 12 squares total. Transfer 6 squares to each of the foil-lined baking sheets.
Slice each of the 2 remaining pastry pieces crosswise into 24 strips, about 3 inches by 1/3 inch, for a total of 48 strips. With pastry brush, lightly brush egg white onto pastry squares. Place thin strips around edges of squares to make border (you will need 4 strips per square).
Bake 1 baking sheet of pastry squares in 400°F oven for 10 minutes or until puffed and lightly colored. Remove. Repeat with second sheet.
While squares are baking, in small bowl, beat together egg yolk, ricotta cheese, sugar, flour and cinnamon. Once both baking sheets of puff pastry have been pre-baked, spoon generous tablespoon of ricotta mixture into center of each. Return both sheets to 400°F oven and bake 10 to 12 minutes more or until cheese mixture is set.
Meanwhile, in small saucepan or in small bowl in microwave oven, melt peach preserves. Once packets have been removed from the oven, top each with 4 peach slices. Brush with preserves. Return sheets to oven for 2 minutes to warm peaches and glaze. Serve packets slightly warm.