Preheat your oven to 200° C (400° F). Line a pie dish with one of the crusts, bake for 5-10 minutes or until the crust is just starting to brown. The reason for this is to prevent the pie from having a soggy bottom crust.
Heat the 1 tablespoon of butter in a large non stick pan on medium high heat, when hot, add the onion and ham, season with salt and pepper as desired. Cook until the ham is starting to brown and the onion is soft. Remove the ham and onion to a mixing bowl.
While the ham is sautéing, measure out the peas and carrots and add to the mixing bowl. Scrub and dice the potatoes to measure 1½ cups, then boil until just tender, about 6 minutes or so, drain, and add the mixing bowl.
Same pan used for the ham, add the ¼ cup of butter and melt that on medium heat. When melted, sprinkle in the flour and mix, stirring constantly until it just starts to brown, then pour in the milk and cheese. Stir until the sauce is thickened and smooth, and the cheese is melted. Taste and season with salt and pepper as desired, to taste.
Add the cheese sauce to the mixing bowl and mix to combine.
Pour the mixture into the prepared pie crust and spread out evenly.
Top with the second crust, flute as desired. Melt the final two tablespoons of butter and brush the top crust. Cut several slits across the top.
Bake for 45-55 minutes or until the top is golden brown. Remove from oven and allow to cool on a rack for 5-10 minutes, this also sets up the sauce a little.
Cut and serve.
Enjoy.