Make the brine: Combine the water, soup base, fish sauce, and sugar in blender and blend until the sugar is dissolved, 15 seconds. Combine the ribs and brine in an oversized heavy duty Ziploc bag, seal, and brine for a minimum of 8 hours and up to 24.

Separate the brine from the ribs; reserve the brine. Set a roasting rack in a large roasting pan and arrange the ribs on the rack. Bring 6 cups of water to a boil, then carefully pour the boiling water into the pan, cover tightly, set over a burner (or 2 burners) and steam over very low heat until the ribs soften (they’ll be pretty grey; don’t worry!), 1 hour.  While ribs are steaming, bring the reserved brine to a boil in a medium saucepan and reduce to 1 cup, 30 to 35 minutes.

Heat a grill or grill pan over medium-high heat. Brush both sides of the ribs with the reduced brine and grill, flipping and brushing every 2 minutes, until charred and caramelized, 8 to 9 minutes. Slice the ribs between the bones and serve with the extra reduced brine.