Make the ice cream. Split the vanilla pod lengthways and scrape out the seeds. Put them in a medium saucepan with the cream and the sugar and heat to dissolve the sugar.
Whisk the egg yolks in a bowl. Whisking continually, pour the cream mixture over the yolks, return to the pan and heat gently, without allowing the mixture to boil, until just thickened. Transfer to a freezer-proof container and freeze.
Put the nuts, sugar and butter in a small saucepan and cook for 1–2 minutes, stirring, until the sugar has caramelised. Remove from the heat stir in the berries, then tip the mixture on to some greaseproof paper. When it is cold tap with a rolling pin to break into pieces. Serve the ice cream with the pecans and mixed berries.