You can use any fruit of your choice. I have also used strawberries and raspberries. I think even the frozen mixed berries would be good.
Fruit Filling
Ingredients
2 C fresh or frozen blueberries
1 C of sugar ( I prefer 3/4C)
1/4C water
1/4 C cornstarch
3 T water
Instructions
Combine the first three ingredients in a medium saucepan and cook over low heat until berries are soft. Combine the cornstarch and 3 T of water, stirring well. Add to the blueberry mixture; cook, stirring constantly, until thickened. Set aside to cool.
This worked really well with apples!