This is a classic pâtissérie-style fruit tart made with a sablé Breton base – the salt (fleur de sel) comes from Brittany. The base is thick, buttery and crisp, and is easy to make in a sandwich tin, and the berry topping is the very essence of summer.
Make the sablé dough. Sift the flour, baking powder and salt together into a bowl.
Beat the butter in the bowl of a stand mixer fitted with the beater, on medium speed for 2–3 minutes, until soft and creamy.
In a separate bowl, whisk together the egg yolks and caster sugar until thick and mousse-like, and the mixture leaves a ribbon trail when you lift the whisk. Using a wooden spoon, beat in the softened butter until fluffy. Fold in the flour mixture to make a dough, then wrap the dough and chill it for 1 hour.
Make the meringue kisses. Heat the oven to 120°C/100°C fan/250°F/Gas ½. Tip the egg white into a large, clean bowl and, using an electric hand whisk, whisk it slowly until small bubbles form. Increase the speed to medium and beat until white and foamy.
Increase the speed to high and add the caster sugar, 1 teaspoon at a time, whisking well between each addition. Add the salt and continue whisking until you have added all the sugar and the meringue is smooth, glossy and very stiff.
Spoon the meringue into the small piping bag fitted with a small open star nozzle. Pipe small ‘kisses’ onto the lined baking sheet in neat rows, leaving a little space between each meringue: squeeze lightly on the piping bag without touching the baking paper, then pull up quickly to create the tip of the kiss. (You’ll have more kisses than you need. They will keep in a sealed container for up to 5 days –eat them as treats just as they are, or use them to decorate other bakes.)
Bake the meringue kisses on the middle shelf for 45 minutes, until dry and they peel easily off the baking paper. Remove them from the oven and leave them to cool on the baking sheet. Leave the oven on.
Make the raspberry jam. Tip the raspberries and 75g of the sugar into a pan and mash with a potato masher, then place the pan over a low heat and slowly bring the liquid to the boil.
Mix the remaining 45g of sugar with the pectin in a small bowl, then whisk this into the contents of the pan. Continue to boil until the raspberry mixture reaches 105°C on the sugar thermometer. Remove the pan from the heat and carefully pass the jam through a sieve into a heatproof bowl. Leave to cool and set.
Increase the oven temperature to 180°C/160°C fan/350°F/Gas 4.
Roll out the chilled sablé dough to a 20cm-diameter disc. Place the pastry disc in the prepared tin and bake it for 20–25 minutes, until risen and golden brown.
Meanwhile, make the chocolate decorations. Melt 60g of the chocolate in a heatproof bowl set over a pan of barely simmering water until it reaches 44°C on the sugar thermometer. Remove the bowl from the heat and add the remaining 30g of chocolate, stirring until it melts and cools to 32°C.
Using a palette knife, spread a spoonful of the chocolate onto the rectangular piece of acetate. Drag the chocolate comb across the chocolate from the top left-hand corner to the bottom right-hand corner to form diagonal lines of chocolate. Carefully roll the acetate rectangle until the shorter edges are just about touching and place it in the cardboard tube or tall, narrow glass. Leave to set.
Make the pistachio paste. Tip the pistachios into a food processor with the pistachio oil and blitz to a smooth paste, scraping down the inside of the processor bowl as necessary. Add the pistachio extract and blitz for a further 30 seconds, then set aside.
Make the crème mousseline. Pour the milk into a pan, add the vanilla seeds and bring the milk to the boil.
Meanwhile, in a mixing bowl, whisk the egg yolks and caster sugar together, then add the flour and whisk until smooth.
Pour the hot milk over the egg mixture, whisking continuously, then pour the mixture back into the pan and heat it until it comes to the boil again. Reduce the heat and simmer for 3–5 minutes, until smooth and the mixture no longer tastes floury.
Pour the mixture into a clean bowl and cover the surface with cling film to prevent a skin forming. Leave to cool, then transfer to the fridge and chill for 1 hour, until set.
Remove the chilled mixture from the fridge and place it in the bowl of a stand mixer fitted with the whisk. With the whisk on low speed, add the butter, a little at a time, until combined, then fold in the pistachio paste. Spoon the mixture into the medium piping bag fitted with a small plain nozzle and chill until needed.
Make the glaze for the sablé. Place 2 tablespoons of the set jam into a small pan with 3 tablespoons of water. Over a low heat, bring the mixture slowly to simmering point, stirring until smooth, then remove the pan from the heat and set aside.
To assemble, spread the remaining jam over the baked sablé round, leaving a 1.5cm border around the edge. Pipe the crème mousseline in a spiral over the jam, working from the outside into the middle, and chill for 15 minutes.
Arrange the strawberries and raspberries on top of the chilled mousseline layer. Using a pastry brush, dab the top of the fruit with the raspberry glaze.
Finally, using a small cake-decorating paint brush, top 12 of the meringue kisses with gold leaf, then peel the chocolate spirals off the acetate. Decorate the sablé Breton with the meringue kisses and chocolate spirals.