In a mixing bowl, combine the flour and salt, then cut in the butter until it resembles coarse crumbs.

Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.

Boil the cubed potatoes in salted water until tender, about 15 minutes.

Drain the potatoes and return them to the pot. Add the milk, sour cream, garlic powder, onion powder, salt, and pepper, then mash until smooth.

Preheat your oven to 375°F (190°C).

On a floured surface, roll out the dough into a circle large enough to fit your pie pan, about 1/8 inch thick.

Transfer the dough to the pie pan and fill with the mashed potato mixture, smoothing the top.

Bake the potato pie for 45 minutes or until the crust is golden brown.