For the lemon curd, heat lemon juice and butter in a saucepan set over medium heat until butter has melted, stirring regularly. Whisk in remaining ingredients until combined. Cook for about 6-8 minutes or until mixture is thick and glossy, whisking constantly. Transfer mixture to a bowl, and directly cover surface with plastic wrap. Set aside to cool completely. Transfer mixture to a piping bag, and refrigerate until needed.⏱ 8 min
For the lemon curd ice cream, place milk, lemon zest, vanilla bean and seeds in a saucepan set over medium heat, and bring up to a simmer.
Meanwhile, whisk sugar and egg yolks in a bowl until thick and pale.
Gradually pour milk mixture into bowl with egg mixture, whisking constantly to combine.
Transfer mixture to a clean saucepan and place over medium heat. Cook until mixture slightly thickens, and coats the back of a spoon, stirring constantly.
Strain custard through a fine sieve into a large bowl set over an ice bath, and set aside to cool completely, stirring occasionally. Stir in lemon juice to combine.
Churn custard in an ice cream machine according to manufacturer's instructions. Transfer mixture to a tray about 4cm deep, and randomly pipe dollops of lemon curd into the ice cream.
Place ice cream in freezer until firm and ready to serve.
For the sable, preheat oven to 170C, and line a large tray with baking paper.
Beat butter, sugar, and vanilla seeds in the bowl of an electric mixer until thick and pale. Beat in egg yolk until well combined, then mix in flour and salt until combined.
On a lightly floured surface, roll out dough to 4mm-thick, then carefully transfer to tray. Bake in oven for 8 minutes or until golden. Set aside to cool completely. Once cooled, crumble biscuit. Store in an airtight container until needed.⏱ 8 min
For the souffle, preheat oven to 200C.
Lightly grease souffle moulds with butter. Refrigerate until set, then repeat process, brushing generously up the sides and in the crease at the top. Dust moulds with sugar until evenly coated. Additionally, spray oil around rims of moulds.
Place milk, vanilla bean and seeds, and lemon zest in a saucepan set over medium heat, and bring to the boil.
Meanwhile, using an electric mixer set to high, whisk egg and 1 yolk until aerated. Gradually add 75g of the sugar to bowl, whisking until thick and pale. Decrease speed to low, sprinkle in flour, and whisk until smooth. Slowly add milk mixture, whisking until combined. Transfer mixture to a clean saucepan, and place over medium heat, discarding vanilla bean. Cook for about 3-4 minutes until thickened and mixture is coming away from the sides of the pan, stirring constantly. Remove from heat and allow to cool slightly.⏱ 4 min
Add remaining 6 egg yolks, and stir to combine, then add butter and stir to combine. Transfer mixture to a bowl, place plastic wrap directly onto the surface, and set aside to cool slightly, then refrigerate to cool completely.
Place egg whites into the bowl of an electric mixer fitted with a whisk attachment. Beat whites until frothy, then gradually add remaining 125g caster sugar, and beat to soft peaks.
Fold half of the egg white mixture into the souffle base mixture until well combined, then fold through the remaining egg white mixture.
Half fill moulds with the souffle mixture. Place a spoonful of sable crumbs on top of the mixture, then pipe lemon curd over the top. Spoon in remaining souffle mixture until about 1.5-2cm from the top of the moulds. Place moulds onto a tray, and bake in oven for 3-4 minutes. Remove from oven, sprinkle surface with sable mixture, then return to oven for a further 4-6 minutes or until golden and they have risen about 3cm above the rim of the moulds.⏱ 10 min
Remove from oven, dust with icing sugar and serve with ice cream.