Cook the mussels by shaking them over the fire for 5-6 minutes in a dry sauce-pan. Remove from the shells. Steam the spinach, or boil it with a minimum of water. Squeeze out the liquid and stir in a little butter.
On buttered bread lay a "stripe" of scrambled egg, next, in the middle, a row of mussels, and finally a "stripe" of spinach. The result will be an attractive and tasty sandwich.