Whip the Isigny crème fraîche with the single cream, sugar and lemon zest. Pour into a dish and set aside in the freezer for 3 or 4 hours, stirring every 15 minutes.
While the ice cream is resting, wash and halve the apricots. Melt the butter in a frying pan over a medium heat and add the rosemary sprigs and apricots. Cook the apricots, stirring regularly. Add the brown sugar and leave to caramelise for a few minutes. Drizzle with the butter.
Serve a scoop or quenelle of ice cream on each plate with some roasted apricots.
