In a heavy bottom skillet, brown sausage over medium heat. Add a little oil to the bottom of the pan if it sticks, add a little oil and break it up with the back of a wooden spoon. Cook until all the pink is gone. With a slotted spoon, remove the sausage from the skillet into a bowl.
Remove the inside of the potatoes and place a bowl with the Parmesan. Mash with a potato masher until they are smooth. Add the egg, sour cream, 1/4 cup panko bread crumbs, and season with salt and pepper. Add sausage to the bowl with the potatoes 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-inch thick.
Add 1 cup panko bread crumbs to a 13 by 9-inch casserole dish and add chopped parsley and stir to combine. Dredge croquettes through the panko mixture and 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 degrees F oven while you prepare the eggs and hollandaise.
For the Hollandaise Sauce: Add yolks, mustard and heavy cream to a blender. Blend until the egg yolks look light yellow and foamy about 1 minute. Keeping the blender on, slowly stream in the melted butter, making sure it emulsifies fully. Keep blending and add a pinch of salt and pepper, lemon juice, cayenne and hot sauce. Blend again until fully incorporated, then add chives at very end. Keep warm.
For the eggs: Add oil to a non stick skillet over medium heat until hot. Add eggs and fry in batches until the whites are set and the yolks slightly runny. Season with salt and pepper.
Lay a small handful of baby spinach on the serving dish and top with pork croquette. Top the croquette with the fried egg and ladle over the hollandaise sauce.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.