Of course, if you use homemade puff pastry will be even better, but with all the work that we have in the typical meetings of the Christmas dates, the use of frozen or refrigerated puff pastry is a good option.
We start by chopping the spinach into very small pieces. In a frying pan, melt the butter and sauté the spinach a little until its volume is reduced by half. Add the flour and mix it with the spinach, stirring while toasting a little.
We are adding the whole milk very slowly while we stir. Little by little we make a thick bechamel that we let cool. Meanwhile, we prepare the fish, splitting the salmon loin into ingots of 100 gr each.
Cut the puff pastry into pieces of approximately 20×15 cm and place the salmon loin in the center. It we cover with the spinach bechamel and we close the puff pastry package forming an ingot. We make a hole in the upper part to act as a fireplace and we varnish with beaten egg. Bake at 200º for about 15 minutes until the packages are golden brown.