Place potatoes and parsnip in a large pot. Bring to a boil and cook until fork tender. Drain.
While potatoes are cooking, cook bacon in a skillet over medium heat until cooked through. Use a slotted spoon to transfer to a paper towel lined plate.
Place cooked potatoes, parsnips, butter, 1/2 cup milk, Parmesan and nutmeg in the bowl of a stand mixer and whip until creamy. Add more milk if desired. Fold in bacon pieces. Season to taste with salt and pepper. Note: You can also use a handheld mixer for this. Serve hot.