FOR THE CRUST:
1. Scrub the potatoes, wrap in foil and bake in a pre-heated 350°F oven for about 45 minutes or until cooked.
2. Peel off skin and mash the potatoes using a potato ricer.
3. Put mashed potatoes in a bowl, and add salt, Parmesan cheese, flour and egg yolk. Mix well, and set aside.
4. Divide mashed potato mixture into 30 equal portions.
BECHAMEL SAUCE
1. Melt the butter in a saucepan.
2. Stir in flour and cook, stirring constantly, until the flour is cooked, about 2 minutes.
3. Add the fresh milk continuing to stir as the sauce thickens.
4. Add the cream and pepper. Do not add salt, as the ham is already naturally salty.
FILLING:
1. Heat the butter in a sauce pan and sauté the onion and garlic until translucent.
2. Add the ham and sauté for about one minute.
3. Add spinach, nutmeg and the prepared béchamel sauce. Lower heat and continue to cook, stirring for about 2 minutes more. Remove from heat and let cool.
4. Divide the filling mixture into 30 equal portions and chill.
TO ASSEMBLE:
1. Using wet hands, roll potato mixture into oval croquettes. Press the center of the croquette to encase the filling.
2. Dredge each croquette in flour, then dip in beaten egg, and coat with breadcrumbs. Arrange on a tray.
3. Pour oil into saucepan, making sure it is 1-inch high up the sides, and heat to 330°. Fry a few croquettes at a time until croquettes turn golden brown. Transfer croquettes to a wire rack set over a baking sheet, and keep warm in the oven while frying the rest. Serve immediately, with lemon wedges on the side.