Preheat your oven to 400F. Heat a high sided pan to medium heat, melt the butter and add in the flour. Whisk to make a roux, and cook for about 1 minute.

Pour in the milk while stirring constantly, to create the bechamel (flour thicknened cream sauce). Bring the mixture to a bubble to fully activate the roux's thickening pour.

When the mixture has thickened, add in the chicken, onion, veggies, potatoes, nutmeg and thyme. Season with salt and pepper to taste.

Split the filling between the 2 10 ounce ramekins. Now, you have several options for the crust. You can resort to sheer laziness, like me, and just lay a circle of the puff pastry dough on top of the filling. You an also cut a disc larger than the ramekin, and completely cover the pie by brushing egg wash around the rim and pressing the dough around the edge of the ramekin. Either way, do as your heart desires. Just make sure to vent the dough by cutting a small slit in the middle, if you're covering the whole thing. Brush the pastry with a bit of the beaten egg, to promote browning.

Bake at 400F for 20-25 minutes, or until the curst is golden and puffed. You can also broil the top for a few minutes to promote browning.