Roll the pastry out thinly on a lightly floured surface and use to line 6 buttered 10 cm (4 inch) fluted loose-bottomed tart tins, rekneading and rerolling the pastry trimmings as needed. Trim off the excess pastry from the top of each tart with scissors so that it stands a little above the tin. Put on a baking sheet and chill for 15 minutes.
Rinse the spinach well, drain in a colander, then dry-fry with just the water clinging to the leaves for 2–3 minutes until the leaves have just wilted. Scoop out of the pan with a slotted spoon, pressing out any excess moisture, then finely chop the leaves.
Drain and dry the pan, then heat the butter and fry the onion for 5 minutes until softened. Stir in the garlic, cook briefly, then return the spinach to the pan. Season with nutmeg and salt and pepper.
Beat the eggs in a bowl, add the crème fraîche and mix until smooth, then mix with the spinach. Divide between the tarts and sprinkle with the pine nuts.
Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 20 minutes until the filling is set and the pine nuts are golden. Check after 15 minutes and cover the tops of the tarts loosely with foil if they seem to be browning too quickly. Leave to cool for 5 minutes, then remove from the tins and serve with a green salad.