Preheat the oven to 220°C, fan 200°C, gas 7.
On a lightly floured surface, roll out the pastry to a rectangle, about 5mm thick, then cut into 6 rectangular pieces. Using a knife, score a border about 1cm inside the edge of each pastry rectangle. Bake on baking sheets for 12 minutes.
Meanwhile, use a pestle and mortar to crush the garlic and salt to a purée, then mix in the olive oil. Heat the garlic mixture and butter in a large frying pan. Once melted, add the mushrooms and thyme. Sauté for 5-8 minutes, until softened. Add the wine and bring to the boil, then add half the crème fraîche and bring to the boil again. Remove from the heat.
When the pastry cases are cooked, push down the centres. Brush the edges with beaten egg and fill the cases with the mushroom mixture. Turn down the oven temperature to 200°C, fan 180°C, gas 6.
Divide the remaining 100ml crème fraîche between the pastry cases, then top with the pine nuts. Bake for a further 8-10 minutes and serve warm. These tartlets go particularly well with a crisp salad.
Cook’s tip: These tarts also work well with chestnut and button mushrooms.