Heat butter in a saute pan over medium heat. Saute onion until tender and golden. Whisk in flour, seasoning, salt and pepper. Slowly add chicken broth and then milk, stirring to combine. Cook until thick and bubbly. Add turkey, vegetables, thyme and parsley flakes.
Pour filling into 6 to 8 (depending on the size) individual ramekins.
Cut puff pastry into squares to fit the tops of each ramekin. Place pastry on top of each ramekin, then cut a steam vent in the center of each. Place ramekins on a cookie sheet to catch drips while baking.
In a small bowl, beat egg with fork. Use pastry brush to spread egg wash on pastry.
Bake at 400 degrees for about 15 to 20 minutes, or until pastry is golden brown and cooked through.