Step 1

For hazelnut pastry, finely process hazelnuts in a food processor, add flour, sugar and a pinch of salt, and process to combine. Add butter, process to fine crumbs then add yolks and process until dough just comes together. Form into a disc, wrap in plastic wrap and refrigerate overnight.

Step 2

For poached pears, bring wine, sugar, rinds, juices, thyme, cinnamon and 1 litre water to the boil in a saucepan over medium-high heat, stirring to dissolve sugar. Add pears, cover directly with baking paper, weight with a plate, reduce heat to medium and simmer until tender (25-30 minutes). Remove 6 pear quarters with a slotted spoon, pat dry with paper towels, halve each lengthways and set aside. Refrigerate remaining pears in syrup.

Step 3

Roll pastry out on a lightly floured surface to a 3mm-thick round, then line a 23cm-diameter, 3cm-deep tart tin and trim edges. Refrigerate to rest for 1 hour, preheat oven to 180C and blind-bake tart case until edges are light golden (6-8 minutes). Remove paper and weights, then bake until light golden and crisp (5-6 minutes).

Step 4

Meanwhile, heat butter in a saucepan over medium heat until golden brown and fragrant (3-4 minutes), pour into a bowl and set aside. Whisk eggs, yolk, sugar, vanilla seeds, rind, thyme and a pinch of salt in an electric mixer until fluffy (2-3 minutes), then whisk in flour on low speed. Whisk in brown butter and crème fraîche, pour into pastry case, arrange halved pear wedges on top and bake until set and golden (45-50 minutes). Cool a little, then scatter with extra thyme and serve warm or at room temperature with crème fraîche and extra pears in syrup. This tart is best eaten on the day it's made.