Mix the seafood together with the orange juice, cilantro, fresh chile, oil, chipotle, and salt and let the mixture marinate for about 20 minutes.
Meanwhile, mash the onion, chile, salt (the coarseness of kosher salt helps you make the paste), and half of the cilantro to a paste in a molcajete or other mortar. You can also mince and mash the ingredients together on a cutting board with a large knife or a fork, and then transfer the paste to a bowl.
Score the flesh in the avocado halves in a crosshatch pattern (not through the skin) with a knife and then scoop it with a spoon into the mortar or bowl. Toss well and mash coarsely with a pestle or a fork. Season to taste with lime juice (if you'd like) and additional chile and salt.
With a slotted spoon, transfer about half of the seafood mixture into the guacamole, and stir.
Season to taste with additional salt, then garnish with the remaining seafood mixture and the reserved cilantro.
The seafood mixture and the guacamole (with a piece of plastic wrap pressed against the surface) can be stored separately in the refrigerator for up to an hour. Let the guacamole come to room temperature and let the seafood mixture stand at room temperature just long enough to take some of the chill off before you assemble and serve the guacamole.
Reprinted with permission from Truly Mexican by Roberto Santibanez with JJ Goode, copyright (C) 2011. Published by Wiley.