Puff pastry with mushrooms

1. Preheat the oven to 200°C (gas level 6-7).
2. Clean and slice the mushrooms. Finely chop the shallots and garlic.
3. Heat the butter and oil in a pan. Fry the shallots until translucent.
4. Add the mushrooms and fry over high heat until all the liquid has evaporated and the mushrooms begin to brown.
5. Add the minced garlic and chopped parsley. Season with salt and pepper.
6. Add the crème fraîche, mix well and reduce for 2 to 3 minutes for a smooth but not too thin filling. Allow to cool slightly.
7. Place the puff pastry squares on a baking tray lined with baking paper.
8. Spoon a generous spoonful of mushroom filling into the center or half of each square.
9. Fold the dough into a triangle or rectangle, or fold the corners inward to form a basket shape. Glue the edges together thoroughly with a little water.
10. Brush the top with the beaten egg yolk diluted with a little water for a golden color.
11. Bake for 20 to 25 minutes. The dough should be well risen and golden.
12. Serve warm with vegetable salad.