Heat a large skillet over medium heat, and melt the butter in it. When melted, whisk in the flour until the mixture's uniform and paste like in consistency. Let it cook, whisking constantly for 30 seconds to cook out the floury taste.
1/4 cup butter, 1/4 cup flour
Whisk in the milk, a little at a time, then add the broth and the thyme, and whisk the mixture constantly for 6-8 minutes- until it's smooth, bubbling, & thickened.
3 cups whole milk, 1/2 cup chicken stock, 1/2 tsp dried thyme
Add the ham and the veggies, stirring to completely incorporate. Let the mixture simmer for another 5 minutes, until the veggies are heated through. Pour the mixture out into a deep, lightly greased 9" pie dish. Use a spatula to spread it out evenly.
2 cups chopped cooked ham, 1 10 oz pkg frozen peas & carrots, 1 cup frozen green beans; thawed, 1/2 cup frozen corn kernels; thawed
Unroll the pie crust, and spread it out evenly over the top of the dish. Crimp the edges to seal the dish closed. Use a sharp knife to cut three slits in the top of the crust.
1 refrigerated pie crust
Bake the dish at 450 degrees for 35-40 minutes, or until the filling is bubbly & the crust's a perfect golden brown.