Combine pie filling, milk, salt and nutmeg and cook while mixing until thick.
Combine rhubarb, sugar, strawberries and let sit.
Prebake pie crust for about 15 minutes.
Add pie filling, top with rhubarb, strawberry mixture, top with slices of puff pastry and if preferred, can weave to make a lattice on top of the pie. Cut off excess dough. Sprinkle top of pie with large granueled sugar and bake for another 30 minutes.