Prepare basmati rice according to package directions.
Cook curry powder in a medium skillet over medium heat about 30 seconds or until fragrant. Add oil, and cook, stirring constantly, 1 minute. Add onion, and sauté 1 minute. Stir in lemon juice. Add rice, chicken, salt, and pepper; cook 1 minute.
Roll one pastry sheet into a 12-inch square on a lightly floured surface. Cut pastry into 9 (4-inch) squares.
Stir together egg and 2 tablespoons water; lightly brush edges of pastry squares with mixture.
Place 2 tablespoons rice mixture on each square, and fold over to form a triangle. Press edges to seal. Repeat procedure with remaining pastry and filling. Brush tops with remaining egg mixture, and place on a baking sheet.
Bake at 400º for 20 minutes or until golden brown. Serve warm with chutney.
INDIAN PARTY POCKETS: Stir 1/3 cup golden raisins, 1/4 cup chopped almonds, and 3 tablespoons chopped cilantro into prepared chicken mixture, and proceed as directed. For a creamy dipping sauce, stir 1 cup plain yogurt, 1 tablespoon chopped cilantro, and 1/4 teaspoon each of curry powder, ground red pepper, salt, and pepper into the mango chutney.
NOTE: To make smaller appetizers, cut each pastry sheet into 16 (3-inch) squares, top with about 1 tablespoon rice mixture, and proceed as directed.