In a heavy bottomed skillet, brown sausage over mediium heat. Add a little oil to the bottom of the pan if sausage sticks and break up with the back of a wooden spoon. With a slotted spoon, remove the sausage from the skillet to a bowl.
Remove the inside of the potatoes and place in a bowl with the Parmesan. Mash with a potato masher until smooth. Add the one, lightly beaten egg, sour cream, 1/4 cup of panko bread crumbs, and season with salt and pepper. Add sausage to the bowl and mix well. With your hands, divide the pork mixture into 1/4 cup portions and flatten so that each croquette is about 1/2 thick.
Add 1 cup of panko bread crumbs to a 13 x 9 casserole dish and add chopped parsley and stir to combine. Dredge croquettes through the panko mixture. Repeat.
Heat a heavy bottomed skillet over medium-high heat. Add enough oil to cover the bottom of the pan. Add the croquettes and saute until golden brown and crisp, about 6 minutes per side. Hold in a 200 degree oven while you prepare the eggs.
Add oil to a nonstick skillet over medium heat untiil hot. Add eggs and fry in batches until the whites are set and the yolks are slightly runny (or cooked to taste). Season with salt and pepper.
Lay a small handful of baby spinach onthe serving dish and top with warm pork croquette. Top croquette with fried egg and ladle over the Hollandaise Sauce.