1.Place cream, milk and vanilla seeds in a saucepan over medium heat and bring to a simmer.
2.Meanwhile, whisk yolks and sugar in a large bowl until pale. Add cream mixture and whisk to combine. Return to pan and stir continuously over medium heat until mixture coats a spoon thickly (4-5 minutes). Remove from heat, add chocolate and chilli, whisk until smooth and combined, then divide among six, 150ml serving glasses. Refrigerate until completely chilled and set (2 hours).
3.For soured cream, whisk sour cream and thickened cream in a bowl until stiff peaks form, then fold in lime zest. Refrigerate until ready to serve.
4.Serve topped with a dollop of soured lime cream, extra grated chocolate and lime zest, with biscotti for dipping.
