1. Preheat oven to 375 degrees. Thoroughly scrub potatoes. Poke a few holes in the potatoes on each side. Rub the potatoes with olive oil and sprinkle with salt. Place the potatoes directly on the middle rack to bake. Place a baking sheet on the rack beneath the potatoes to catch any drippings. Bake for about an hour (maybe additional time, depending on your oven), until the potatoes are tender, when squeezed. Cut in half and allow to cool.
2. Cook the chopped bacon until crispy in a large saucepan. Using a slotted spoon to remove the bacon onto a paper towel. Leave the bacon drippings in the pan. Add the chopped onions to the bacon drippings and cook, over medium-low for about 5-7 minutes, or until the onion is translucent. Turn off the heat.
3. When the potatoes are cool enough to handle, scoop out the potato pulp and add to the onion mixture. Save the potato skins for later use (potato skins). Gently smash the potatoes ( I like them chunky). Add the sour cream and milk until the soup reaches your desired consistency. Season with the salt and pepper, to taste.
Over medium/medium-low heat, warm the soup for a few minutes, until it begins to gently bubble. Serve topped with shredded cheddar cheese, crumbled bacon, and chopped scallions.