I use a dutch oven for this recipe.
To make the crust, combine the almond flour, arrowroot, eggs, cold water, baking powder, and salt in a food processor and pulse four or five times, until combined. Add the butter in half tablespoon pats spaced out evenly around the bowl. Pulse four or five times more, just until the butter is incorporated and you have pea-size bits of dough. Using your hands, form the dough into a ball, wrap it tightly in parchment paper, and chill in the freezer for 30 minutes.
Sauté the carrot and celery in 2 T butter until tender.
In a large soup/stock pot whisk the arrowroot powder into the milk and heat until thick. Stir in the cream and heat again until thick.
Add the seasonings, peas, corn if using, broccoli, carrots, and celery to the cream base. Stir in the turkey or chicken.
Roll out the dough between two sheets of parchment paper into a circle 1/8 inch thick. Carefully lay the dough over the filling in your pot, tucking the excess edges inside the pan. Cut a slash with a knife on top of the dough for venting. Brush the dough with the egg beaten with water if desired.
Bake in a 350° F oven for 40-45 minutes, until the crust is golden and the filling bubbling. Allow to rest on a wire rack for 10-15 minutes before serving.