How to Make It
Set the salmon fillet in a glass or ceramic baking dish. Brush the fish all over with 1/4 cup of the mezcal, then cover with plastic wrap and refrigerate for 1 hour.
In a spice grinder, combine the dried chipotles with the kosher salt and grind to a fine powder. Sprinkle both sides of the salmon with the chipotle salt, then cover with plastic wrap and refrigerate for 4 hours longer.
Brush the salmon with the remaining 1/4 cup of mezcal and tightly wrap the fillet in plastic. Refrigerate for at least 4 hours or overnight.
Unwrap the salmon. On a work surface, using a very sharp, thin knife, cut the fish at an angle crosswise into very thin slices. Arrange the slices on a platter.
In a blender or food processor, puree the cream cheese with the lime juice and 2 tablespoons of water. Season with salt. In a bowl, toss the sorrel with the red onion and the dressing. Serve the salad alongside the salmon.
If sorrel is unavailable, use baby spinach.