For the remoulade
1 Tbsp capers, finely chopped
25g cornichons, finely chopped
1 tsp Dijon mustard
1g leaves flat leaf parsley
salt and freshly ground black pepper
For the lobster and buttermilk marinade
1 small lobster, approx. 600g
1 tsp Cajun spice
For the Cajun mayonnaise
¼ tsp Cajun spice
To finish the lobster
reserved marinated lobster
2 sub rolls
1 tomato, cut into 4 slices
4 baby gem lettuce leaves, washed
For the remoulade, peel the celeriac and trim into thin matchstick-size batons and combine with the remaining ingredients. Finely chop the parsley and stir well to combine. Season with salt and freshly ground black pepper and set aside. The flavour of this remoulade improves the longer it stands, so it make this ahead of time and store covered in the fridge.
To prepare the lobster, bring a large pan of water to a simmer. Prepare a large bowl of iced water to have on hand. Lay the lobster onto a chopping board and use a large, heavy knife to cut through the lobster head from the natural crease through the centre of the eyes. Twist off the claws and body and discard the head. Pinch the tail of the lobster at the centre part of the tail fan and twist. Pull the piece away carefully and the digestive tract should come away with it, discarding the digestive tract. Skewer the lobster top to tail to which will ensure they cook as straight as possible. Blanch the lobster tail in the boiling water for 2 minutes, and the claws for 7 minutes and transfer immediately into the prepared ice water. Once cooled, drain the lobster and pat dry using kitchen paper. To remove the tail, cut two lines in the bottom of the shell with scissors and gently remove the tail and cut in half lengthways. For the claws, twist each claw into 3 pieces at the joints. Crush the smaller pieces with the flat side of a knife and carefully remove the flesh. Using the back of a knife, hit the claw just behind the pincer to crack the shell in two. Remove the bottom half of the shell. Dislocate the pincer ensuring the small feather shaped cartilage comes away with it. Carefully remove the flesh from the remaining shell ensuring the large feather shaped cartilage is removed. Check that all shell is removed from the lobster pieces and pat dry using kitchen paper. Make the marinade by combining the buttermilk and Cajun spice together. Add the lobster flesh to the marinade and place in the fridge, covered, overnight.
To make the Cajun mayo, simply mix the mayonnaise and Cajun spice and season with salt and freshly ground black pepper. Set aside.
To finish the lobster, grill the lobster pieces on a hot Fusion BBQ (2-3 minutes on each side for the claws; 6 minutes for the tail), turning regularly. Remove from the grill and season with lemon juice and salt.
Chop the lobster into smaller pieces and mix in a bowl with the Cajun mayonnaise. Toast the rolls and spread a tablespoon of the remoulade on the bottom of each roll. Lay the tomato slices, followed by the lettuce leaves on the roll. Fill the sub with some of the lobster mix.