Wash the pork tenderloin and pat dry. Drill a hole in each fillet with the help of a wooden spoon handle. Peel and finely chop the onion. Fry the onion briefly in 1 tablespoon of hot oil.
Add the spinach and 2 tablespoons of water. Season with salt, pepper and nutmeg, steam for about 10 minutes. Let cool down briefly. Mix spinach and cream cheese. Fill into the fillets with the help of a wooden spoon.
Season the fillets with pepper and wrap each with 3 slices of bacon. Heat 2 tablespoons of oil in a pan. Brown the fillets all around. Sprinkle with dried oregano. Fry over medium heat for about 15 minutes, turning occasionally.
In the meantime, bake croquettes in a preheated oven according to the package instructions until golden brown. Remove the fillets from the pan and wrap them in aluminium foil. Deglaze the meat with 200 ml water and white wine, cook for about 3 minutes.
Stir cream and flour until smooth, thicken sauce with it. Let the sauce simmer for about 5 minutes. Season to taste. Cut fillet into slices. Arrange everything and garnish with oregano.