Place the fry pan over medium-high heat and add the butter to the drippings. When it has melted, add the potatoes and cook, stirring and rolling the potatoes in the pan, until they begin to crisp and brown, 5 to 7 minutes. Add the bacon, reduce the heat to medium-low, and cook until the bacon is hot and the potatoes are very crisp, 2 to 3 minutes. Season with the 1/4 tsp. salt and the 1/2 tsp. pepper and toss well. Add the parsley and toss again. Taste and adjust the seasonings with salt and pepper. Serve hot. Serves 8 to 10.