Take the puff pastry out to thaw

For the bechamel:

In a small pot, over medium heat, warm the milk, bay leaf, pepper and nutmeg

In a separate pot, melt butter then add flour, stirring constantly 

Let it cook a minute or two then slowly add warmed milk, whisking constantly so no lumps appear

Bring to a boil, whisking constantly and then turn it down and let it simmer a bit until thickened

Remove bay leaf

For the filling:

In a Dutch Oven or large skillet, melt butter, add carrots and onions, saute on medium for about 5 minutes

Add celery and garlic and saute for about 10 minutes or until carrots soften

Add bechamel to vegetables and heat through

For the pie:

Lightly flour a work surface

Unfold pastry and roll out until it’s slightly bigger than the pie pan

Place filling in pie pan and cover with pastry, trimming the overhang and sealing the edges

Cut a hole for ventilation in the middle of the pie

Bake in a 375 degree oven for 15 or 20 minutes or until it starts to brown