Preheat your oven to 425° F.
While oven preheats, prepare your apples. Peel and core apples.
Slices apples into about 16 even slices and then chop to dice. They should be small chunks.
Once oven is heated on a sheet pan lined with parchment paper place your frozen puff pastry shells. Before placing in oven you may, optionally, brush the top of shells with egg wash and sprinkle with coarse sugar.
Place sheet pan on middle shelf of oven and cook for 18-20 minutes until golden brown or according to box's directions.
While shells bake cook down apples. Start by melting butter in pan on medium heat. Add in chopped apples and cook for 2-3 minutes until slightly softened. Add in brown and white sugar and cinnamon.
Continue cooking down apples while sugars melt. While consistently stirring cook down for about 5 minutes. To thicken extra moisture released from apples add in cornstarch.
Continue cooking for about 5 more minutes on medium to low heat until apples are softened and sauce is thickened.
Once apples are cooked and shells are baked you may begin assembly.
Start by using a knife to remove tops off pastry shells once they are out of the oven. Fill the opening with warm apple filling.
Plate them up and dust with powdered as garnish. Serve immediately when warm, but they also taste delicious cooled.
Enjoy!