Heat the oven to 275°F.

Rinse and pick over your chicken livers, removing any large veins or little green blobs of bile. Don't worry about keeping the livers intact and pretty; they're going into the food processor.

Put the garlic and shallots in the work bowl of the food processor and pulse on and off until finely chopped. Scrape them out into a medium mixing bowl. Return the work bowl to the processor (no need to clean it) and add the chicken livers. Pulse the machine on and off until the livers are chopped coarsely but evenly. Add them to the mixing bowl with the garlic and shallot, then add the pork, 5-spice, fish sauce, sugar, and salt. Mix gently but thoroughly. (A rubbergloved hand is the best tool for this.)

Pack the mixture into a baking pan with a 6-cup capacity—like a terrine mold or an 8½-by-4½-inch loaf pan. Set the terrine in a deep roasting pan and add hot tap water to come up nearly to the lip of the terrine pan. Put the terrine in its water bath in the oven and bake for 1 hour and 15 minutes, or until an instant-read thermometer stuck into the middle of the terrine registers 145°F.

Remove the pan from the bath and put it on a cooling rack. Allow the terrine to cool to room temperature, then wrap the pan in foil and put it in the refrigerator to thoroughly chill, at least 1 hour or overnight.

Remove the terrine from the refrigerator and unmold it: Lay a couple pieces of plastic wrap over your counter. Run a knife (a butter knife is fine) under hot water, then run it along the edges of the terrine. Invert the pan onto the plastic wrap, rapping the pan against the counter if the terrine doesn't immediately release itself. You can use the terrine now or wrap it in the plastic and store it in the refrigerator for up to a week. Or, if you're making this far in advance or don't anticipate making that many sandwiches, cut the terrine into whatever size pieces suit your purposes, wrap well, and freeze. Frozen, the terrine will keep for months. Defrost it as you would any meat, still wrapped and in the refrigerator, allowing at least a couple of hours per pound of frozen terrine.