Spinach au gratin

Poach all the vegetables, except the spinach and mushrooms, with a dash of oil.

Add the mushrooms and the "tails" of the spinach (if fresh spinach is used) to the previous vegetables.

When almost done, add the spinach leaves and season with salt and pepper.

Drain it, to remove the water released by the vegetables.

To make the béchamel sauce, heat the oil with a few slices of onion until golden brown and then remove the onion, add the flour, sauté it, add the milk. Stir it all until the béchamel sauce is made without lumps. Add a pinch of salt and nutmeg.

Mix the béchamel sauce with the vegetables, which were draining, in the same pan as the béchamel sauce.

Put it in a baking dish suitable for the oven.

Beat the egg, pour it on top and gratin it in the oven, previously heated to 180ºC, only heat up.

When the egg is toasted, remove from the oven.