Pour a drizzle of olive oil and a tablespoon of sugar into a pan. Once the sugar is golden brown, add the chopped onion. Brown the onion and add the fresh spinach. Cook a few minutes and add the raisins, pine nuts and Pedro Ximénez vinegar. Stir and add a pinch of salt.
Rinse the champignons and cut off the bottom of the stalks. Place in a pan with a drizzle of olive oil and salt, cook covered. Once cooked, remove and fill with the stir-fried spinach.
Fry the quail eggs and place on the stuffed champignons before serving. Salt and pepper to taste and serve hot.