The Soak: Place the beef riblets in a bowl of lightly salted water. Let them soak for 15 minutes to remove impurities. Drain and wash thoroughly with cold water.
The Marinate: Pat the ribs dry. In a bowl, combine the ribs with the white parts of the green onions, minced garlic, salt, and pepper. Mix well and let marinate for 15 minutes.
The Caramel Base: Place a large, heavy pot on the stove over medium heat. Add the oil and spread the sugar evenly across the bottom.
The "Amber" Moment: Watch the sugar closely as it melts. Once it turns a deep, dark amber brown (the color of a new penny), immediately remove the pot from the heat.
The Coating: Add the marinated ribs to the pot. Stir constantly to coat every riblet in the hot caramel. The sugar may seize slightly; this is normal.
The Deglaze: Return the pot to medium heat. Add the coconut water and fish sauce. Bring the mixture to a boil, stirring to ensure the caramel is fully dissolved.
The Braise: Once boiling, turn the heat down to a low simmer. Cover with a lid and cook for 25 minutes to tenderize the beef.
The Reduction: Remove the lid and stir in the garlic chili sauce. Increase the heat slightly to a steady simmer. Cook uncovered for another 25 minutes, stirring occasionally.
The Finish: When the liquid has reduced into a thick, gooey glaze that coats the meat, pull the pot off the stove.
Serve: Toss in the green onion tops for a final stir. Serve immediately over warm jasmine rice.