In a bowl, combine the grated cheese with the sour cream, then season with a pinch of black pepper and a pinch of nutmeg. Stir for about 1 minute until well combined.
Spread the cheese mixture on one slice of toast bread, then cover with a second slice of bread to form a sandwich.
In a shallow bowl, beat together the eggs and milk for about 1 minute, then season with salt to taste.
Dip each sandwich on both sides into the egg-milk mixture to coat.
Heat the vegetable oil and butter in a frying pan over medium-high heat. Fry the sandwiches for 3-4 minutes on each side until golden brown.