Preheat oven to 400°F.
Melt butter in large skillet over medium heat. Add chopped leeks; cook 1 minute. Reduce heat to low; cover and cook 5 to 7 minutes or until leeks begin to brown, stirring occasionally. Stir in pear cubes and sugar. Increase heat to medium; saute
uncovered until liquid evaporates. Season with salt and pepper. Transfer to bowl; cool. Stir in cheese and chives.
Place puff pastry sheets on work surface. Cut each pastry sheet into 6 squares. Roll out each pastry square to a 3X3 inch square. Place pear/leek mixture on half of each pastry square, dividing equally. Brush pastry edges with egg glaze. Fold pastry over filling. Press edges with fork to seal. Brush turnovers with egg glaze. Pierce pastry in several places with toothpick. Place on baking sheet. Chill 20 minutes.
Bake turnovers until puffed and golden, about 18 minutes. Serve warm.