I found this recipe on Mercotte’s blog, which features a fantastic collection of French (and other) recipes. Mercotte is a frequent guest on the French show Le Meilleur Pâtissier, where contestants compete for the title of France’s best pastry chef. While Mercotte is known for her desserts, she is equally skilled with savory dishes. Her salmon recipe is absolutely heavenly—not only is it very easy to prepare, but it also tastes exquisite, literally melting in your mouth..

Ingredients
1 nice salmon fillet (I used 3 smaller fillets)
1 carrot
1 leek (white part only)
150–200 g fresh spinach
Butter for sautéing vegetables (Mercotte used olive oil)
2 rectangular sheets of puff pastry (42 x 26 cm, to fit the salmon fillet; Mercotte used homemade pastry)
Salt and pepper
1 egg yolk for brushing
Instructions
In a medium pot, bring water to a boil. Add the spinach leaves, stir briefly, then drain immediately. Transfer to a plate lined with a kitchen towel to remove excess water.
Cut the leek and carrot into julienne (thin strips), season with salt and pepper, and sauté in 2 tablespoons of butter. The carrot should remain slightly firm, not completely soft. Set aside to cool.
Preheat the oven to 185°C. Line a large baking tray with parchment paper.
Place one sheet of puff pastry on the tray. In the center, pile the vegetables into a rectangle slightly smaller than the salmon fillet.

Wash and pat dry the salmon fillet, season with salt and pepper, and place it on top of the vegetables..

Evenly distribute the spinach leaves over the salmon to cover it completely.

Cover with the second sheet of puff pastry. Gently press the edges around the fish to seal. Use a knife or pizza cutter to trim any excess pastry around the fish. You can save the scraps to decorate the dish.

Brush the top with the egg yolk, leaving about a 1 cm margin uncoated around the edges. Ideally, refrigerate for 2 hours before baking (I baked mine immediately without chilling).

Bake for 25–30 minutes at 185°C, depending on the thickness of the fillet. My fillet was about 2 cm thick, so I baked it for 30 minutes.
