Preheat oven to 400°F.
Set a pot of water on the stove to boil. Peel the potatoes so the peels come off in strips about an inch wide.
Parboil peels for 3-5 minutes while you chop the potatoes into even-sized chunks.
Lightly grease a pie pan, then place boiled peels in an even layer to cover the entire bottom and sides of the pan.
Spread grated beet evenly over the top of the crust, then dot the top of the vegetables with butter and lightly salt.
Bake crust for approximately 20 minutes, until the vegetables are cooked through and browning.
While the crust bakes, boil the potato pieces and garlic until the potatoes are fork tender – how long will depend on the size of your pieces.
Sauté onions or leeks in a teaspoon of butter.
Combine the remaining butter, cooked onions or leeks, boiled potatoes, garlic, and milk in a bowl and mash manually or mix with a mixer until relatively smooth. Salt and pepper generously, and add a bit of milk if the potatoes are too dry.
Fill the crust with mashed potato mixture. Return to oven for 30 minutes.
Top with crumbled bacon or cheese as desired. Serve warm, cut into slices.