Place a pot of water over high heat and bring to a boil. Peel the potatoes and cut into a large dice. Add the potatoes to the water. Bring the potatoes back to a boil and let cook for 4 to 5 minutes. The potatoes should be soft around the edges but still firm inside. Drain and set aside.
In a large ovenproof skillet, fry the chopped bacon over medium heat until brown and crispy. Remove the bacon with a slotted spoon and set aside. Pour out all but 2 tablespoons of the bacon fat and turn the heat to medium low. Add the parboiled potatoes to the skillet.
Sauté the potatoes for 10 to 15 minutes until they are fully cooked and well browned. In a small cup, stir together the kosher salt, paprika, garlic powder, onion powder, and pepper. Sprinkle the seasoning over the potatoes and cook for another minute. Transfer the potatoes to a platter and set aside.
Add another tablespoon of bacon fat to the skillet along with the diced onion. Season with a sprinkle of kosher salt and cook the onions for 2 to 3 minutes until they begin to soften. Add the mushrooms and season with another sprinkle of kosher salt. Sauté the mushrooms over medium high heat until they begin to brown.
When the mushrooms are brown, return the potatoes and bacon to the skillet. Gently toss the potatoes together and spread out evenly in the skillet.
While the mushrooms are frying, turn the broiler on high. Scatter half of the green onions over the breakfast potatoes and top with the shredded cheese. Broil until the cheese is melted and beginning to brown, about 2 to 3 minutes. Garnish with the remaining green onions. If desired, top with a fried egg and enjoy!