Hazelnut Praline Paris-Brest

Praline. boil the sugar, water and lemon juice without stirring until deep golden, 10-12 min. Stir in the toasted hazelnuts, pour onto the oiled paper and leave 30 min to harden. Break up and process to a fine powder, then add the salt and oil and process 2-3 min to a smooth paste. Take the caramel off when it is deep amber; pale caramel tastes only sweet.

Choux. heat the oven to 200 °C (180 °C fan) and draw a 20 cm circle on the underside of a sheet of baking paper on the tray. Bring the butter, water, milk, sugar and salt to the boil, beat in the flour, then cook on low 2 min until shiny. Cool 4 min and beat in the egg gradually to a glossy paste that falls in a V.

Pipe and bake. pipe a thick ring on the circle, a second ring inside it touching, and a third on top along the join. Scatter with the chopped hazelnuts and bake 40-45 min until deep golden and firm, then turn the oven off and leave 30 min with the door ajar. Cool.

Cream. whisk the yolks, sugar and cornflour; heat the milk to a simmer and whisk it in. Return to the pan and whisk over medium heat until it bubbles for 1 min, past 85 °C. Stir in the vanilla, cover and cool to room temperature, about 1 h.

Whip. beat the butter until pale and fluffy, then beat in the cooled cream a spoonful at a time, and finally 150 g of the praline paste. If the cream looks split, keep beating; it comes together as it warms slightly.

Assemble. split the ring in half horizontally with the serrated knife. Pipe the praline cream in tall swirls over the base, put the lid on and dust with icing sugar. Chill 30 min and serve within 4 h.