Mix together the marinade ingredients in a small bowl until smooth.
Place the salmon skin side up on a work surface and slather with just under half the marinade.
Turn the salmon so it is skin side down onto a large piece of cling wrap. Slather the remaining marinade on the flesh side.
Wrap the salmon in cling wrap. Marinade for 24 to 48 hours.
Scrape the marinade off (do not rinse with water) and leave the salmon to come to room temperature <- KEY for perfectly cooked salmon.
Preheat barbecue plate side on MEDIUM LOW. Leave it to heat up for a good 10 to 15 minutes - another tip for cooking salmon perfectly.
Add oil just before cooking. Place the salmon on the BBQ skin side down. Cook for 3 minutes, then use two spatulas to turn it. Cook the flesh side for 2 - 3 minutes or until caramelised, then flip it again so the skin side is down then transfer to a tray.
Cover loosely with foil to rest for 5 minutes before serving. It will continue cooking while resting.
Garnish with sesame seeds and finely sliced shallots.