How to Make It
To make the marinade: In a mortar and pestle, combine sugar, garlic and chili sauce, mashing them into a paste. Add lime juice and fish sauce. Set 1/4 cup of the mixture aside in the refrigerator. Transfer remaining mixture to a resealable bag, add pork, and set aside in the refrigerator for 2 to 4 hours.
About 30 minutes before serving, make the vegetable mixture: In a large bowl, combine vinegar and salt. Add carrots, radish and onion. Set mixture aside, stirring occasionally, for 30 minutes.
Meanwhile, preheat oven to 450 degrees F. and line a shallow baking pan with foil. Remove pork from marinade (discard marinade), transfer pork to the prepared pan, and roast until the internal temperature is 145 degrees F. (medium rare) to 160 degrees F. (medium), 20 to 25 minutes. Remove pork from the oven and let rest 5 minutes.
Thinly slice the pork. Trim the ends off the baguettes and cut each crosswise into 4 pieces. Cut each piece horizontally, so it’ll open like a book. Gently fold each piece open and spread with mayonnaise. Top with cucumber, pork slices and reserved marinade (drizzle it over the pork), vegetable mixture, and cilantro and serve.