Take a large piece of foil and place the blackberries, raspberries and blueberries or grapes in the middle. Scatter over the caster sugar, lay the vanilla pod on top, then fold the foil into a neat parcel, with the seams at the top.
Once your barbecue is medium hot, place the foil packet on one side of the barbecue, and let the berries cook for 10–15 minutes. Meanwhile, toast your sliced brioche in batches on the other side of the barbecue, cutting them into triangles once toasted.
Divide the lightly cooked fruit between four plates, with the toasted brioche. Add a tablespoon of mascarpone, scatter over the toasted almonds and mint leaves, and serve hot.