Preheat the oven to 180°C (160°C fan oven) Gas Mark 4. Roll out the pastry on a lightly floured surface until big enough to line a deep, 20cm loose-bottomed tart tin. Line the pastry with foil or greaseproof paper, fill with baking beans and bake for 25 minutes. Remove the paper and beans and cook for 10 minutes more until sandy and golden.
Leave the pastry case aside while you make the filling. Melt the chocolate and butter together in a big heatproof bowl over a pan of barely simmering water. Whisk the eggs into the maple syrup, then stir into the melted chocolate with the ground almonds and cinnamon. Stir in the chopped pecans too and pour into the tart case. Arrange the whole nuts on top and bake for 30-40 minutes until set. Serve with good vanilla ice cream or crème fraîche.