Les omelettes en sandwich

For the spinach filling

• 1 pound (450 g) fresh spinach, stemmed and washed
• 2 hard-boiled eggs, peel

Cook the spinach for 3 to 4 minutes in a large quantity of boiling salted water. Drain and refresh in cold water, then drain again thoroughly and squeeze dry in a strong kitchen towel. Chop fairly fine in a food processor or with a knife. Put the hard-boiled eggs through a fine sieve or through the fine disk of a food mill. In the skillet melt the butter, then add the shallots and sauté them ge