Place the salmon on parchment paper and grill at 100 °C for 15 minutes. Adjust the time based on the thickness of the salmon. The goal is to cook the salmon through without browning it like a typical grilled fillet.
Once cooked, let the salmon cool. Flake it gently once it is cool enough to handle. You may notice some white substance on the surface (albumin, a common salmon protein). Scrape it off with a spoon. Discard any brown flesh if present.
Chop the smoked salmon into small pieces and set aside.
In a pan over low heat, melt the butter and sauté the chopped shallots and garlic until the shallots are translucent. Remove from heat and let cool.
In a bowl, combine the flaked salmon, chopped smoked salmon, cooled shallots and garlic, and chives.
Add the Japanese mayonnaise, black pepper, smoked paprika, and smoked salt. Mix until well combined.
Transfer the mixture into a jar and press down with a spoon to eliminate gaps. Cover the surface firmly with cling wrap and refrigerate for at least 2 hours to allow the flavours to meld.
Serve with toast or crackers.