Adjust an oven rack to the middle position and preheat the oven to 400 degrees F.
Pierce the potatoes all over with a fork and microwave on high for 15 to 20 minutes, rotating each potato a few times. The potatoes are done once a toothpick or skewer easily pierces the flesh. Allow the potatoes to cool for 5 minutes.
Meanwhile, lay the bacon in a large nonstick skillet and cook over medium heat, turning once, until golden and crispy, about 5 minutes per side. Transfer the bacon to a paper-towel-lined plate to drain (reserve the drippings in the skillet), then finely chop.
Return the skillet with the bacon drippings to medium heat and stir in the half-and-half, a pinch of salt and 1/2 teaspoon pepper. Cook, stirring, until the mixture is hot and steaming; remove from the heat.
Use a sharp paring knife to cut a lengthwise slit in the center of each potato. Carefully remove enough flesh to leave about a 1/2-inch-thick wall around the inside. Reserve about 1/2 cup of the potato flesh for another use, then add the remaining flesh to a mixing bowl along with the half-and-half mixture, scallion whites, half of the bacon, a large pinch of salt and 2 1/2 cups of the Parmesan. Mash with a potato masher until mostly smooth. Season with additional salt and pepper if needed.
Put the potato-skin shells on a baking sheet. Divide the mashed potato mixture evenly among the skins. Make a large well in each potato deep enough to hold an egg and crack an egg into the well. Bake the potatoes until the eggs are just starting to set, about 10 minutes.
Remove the potatoes and cover the eggs with the remaining 1/2 cup Parmesan. Switch the oven to broil and broil, checking frequently, until the eggs no longer wiggle when you shake the baking sheet, 3 to 5 minutes.
To serve, top each potato with the scallion greens and remaining bacon and serve immediately.
It's important to serve these right away, as the potatoes hold a lot of heat and will continue to cook the eggs if left to sit.