Mashed spinach with onion

Description
In Romanian: Pire de spanac cu ceapa.

Ingredients

 * 3 lb/1,5 kg spinach,
 * 2 tablespoons butter,
 * 1 1/2 cups milk,
 * 1 small onion,
 * 1 teaspoon flour,
 * pinch of sugar,
 * salt

Directions

 * 1) Fry the finely chopped onion in butter, add flour, mix and then pour the milk.
 * 2) Add the cleaned, washed, scalded and finely chopped spinach, salt and sugar and simmer until the liquid is reduced.
 * 3) Serve this dish with French pancakes or croquettes.