Preheat oven to 400 degrees Fahrenheit.
Wash and cut peaches into thin slices. Add slices to a large bowl.
Add sugar, cinnamon and cornstarch to the peaches and stir to coat.
Spread peaches into baking dish. Use any 13x9 inch baking dish or several mini dishes for your preference.
Stretch the thawed puff pastry over a clean work surface. Gently pull the pastry to slightly stream h the dough.
Use a biscuit cutter to cut pieces of pastry. Place the puff pastry over the peaches. These can be slightly overlapping. Use any scrap pieces to fill in the corners if necessary.
Mix egg white with a teaspoon of water. Use a pastry brush or silicone brush to brush the pastry with egg wash.
Sprinkle the teaspoon of sugar over the puff pastry.
Bake cobbler in preheated oven for 35-40 minutes. Peaches should be juicy and softened and pastry will be puffed and golden brown.
Let cobbler cool for 15 minutes before serving. Serve warm with vanilla ice cream or whipped cream.