Shane Osborn: Grilled marron with fennel salad and green olive and vanilla velouté

1.For green olive and vanilla velouté, thinly slice one-third of the olives and set aside. Finely chop remaining olives and combine with fennel, butter, tarragon, shallot, garlic and vanilla in a saucepan over low heat, season to taste, cover with a lid and cook until vegetables are tender (10-15 minutes). Add vermouth and cook over low-medium heat until reduced by two-thirds (20-30 minutes), add stock and simmer until reduced by one-third (20 minutes), then add cream and simmer for 5 minutes. Strain through a fine sieve, season to taste with lemon juice, add remaining olives and keep warm. Makes 375ml.

2.Place marron in the freezer until they are rendered insensible (15-20 minutes), then insert a knife into the base of their heads to kill them humanely. Bring a large saucepan of salted water to the boil. Add marron, bring back to a gentle boil and cook until almost cooked through and bright red (3-5 minutes). Drain and refresh.

3.Meanwhile, preheat a grill to high. Combine fennel, lemon juice and oil in a bowl, season to taste and set aside. Halve marron lengthways through shell, place cut-side up on an oven tray, grill until just cooked though (1-2 minutes). Serve immediately scattered with fennel mixture and drizzled with green olive and vanilla velouté.