Preheat oven to 375F. Roll out pastry on floured surface to 12x9-inch rectangle. Cut pastry in half lengthwise, creating two 12x4 1/2-inch strips. Place 1 pastry strip on large baking sheet. Spread jam evenly over pastry, leaving 1/2-inch border on all sides. Fold remaining pastry strip in half lengthwise. Using small knife and beginning 1/2 inch from 1 end of pastry, cut slit through fold to within 1/2 inch of unfolded side of pastry. Repeat cutting slits at 1/2-inch intervals. Unfold dough and open flat on work surface. Whisk egg and cream in small bowl to blend. Brush cut pastry with some of egg mixture. Brush edges of jam-covered pastry strip with some of egg mixture. Place cut pastry strip over strip with jam, egg-glazed side up. Press edges firmly to seal. Bake tart until pastry is golden, about 25 minutes. Transfer sheet to rack and cool 5 minutes. Using large metal spatula, loosen tart from sheet. Slide tart onto rack and cool completely. (Can be prepared 6 hours ahead. Cover and let stand at room temperature.) Serves 6. Bon Appetit March 1995 Per serving: 117 Calories (kcal); 10g Total Fat; (76% calories from fat); 6g Protein; 1g Carbohydrate; 207mg Cholesterol; 61mg Sodium Food Exchanges: 0 Grain(Starch); 1 Lean Meat; 0 Vegetable; 0 Fruit; 1 1/2 Fat; 0 Other Carbohydrates Converted by MM_Buster v2.0n.