Black Cardamom Prawn Ballotine and Celeriac Sunchoke Bisque

Place the caul fat in a bath of cold water and let sit for 1 hour (this helps remove any impurities and makes the webbing more pliable).
Preheat a water bath to 145°.
Place prawns, fish, cream, salt, black cardamom, and egg in a food processor and pulse for 30 seconds, then leave running for 30 seconds. Stop and scrape down the sides every so often until a smooth paste is formed.
Place a large sheet of plastic wrap on a clean cutting board. Shape a 9x10" rectangle of caul fat on top of the plastic wrap. Spread a quarter of the prawn mixture down the middle of the sheet of caul fat. Roll the caul fat, plastic, and prawn mixture until a large tube is formed. Twist the plastic wrap and make a knot at both ends. You should end up with a large, tight tube. Place tube in preheated water bath and cook for 40 minutes.

Using a peeler and small utility knife, peel and remove both the outer skin of the celeriac and any folds that contain dirt or small pebbles. Then dice the celeriac into rough cubes and place in pot.
Wash the sunchokes thoroughly, making sure to remove any bits of dirt. Dice into pieces roughly the same size as the celeriac and place into the pot.
Add the shallots and cream. Pour in filtered water until the liquid covers over half an inch.
Turn on medium-high heat and simmer until root vegetables are tender.
Reserving the liquid, strain the vegetables and place them in a high-powered blender. Add the butter, vinegar, and reserved liquid, pulsing until silky smooth. Use a spoon to test (should completely coat spoon when dipped and removed from bisque). Add white pepper and salt to taste.
Serve bisque topped with tarragon oil, celery-compressed apple, frisée, and lavender.