Combine all ingredients in a small saucepan or skillet.
Cook over medium heat, stirring until the sugar is fully dissolved.
Simmer for about 5 minutes until the sauce thickens slightly.
Turn off the heat and let it cool.
Soak rice noodles in room temperature water for 15 minutes. Drain and set aside.
Heat a little oil in a wok or pan. Sear the prawns until almost cooked through, then remove and set aside. (Tip: Lightly press the shrimp heads to release their flavorful fat.)
In the same pan, add a bit more oil. Stir-fry shallots, tofu, dried shrimp, and salted radish until fragrant. Push to one side, crack in the egg, and scramble.
Add the soaked noodles and prepared Pad Thai sauce. Stir-fry until noodles are soft and well coated. Add a splash of water if needed to soften the noodles.
Add back the prawns, then toss in bean sprouts and garlic chives. Stir just until just combined, then remove from heat.
Plate the Pad Thai and top with the prawns. Serve with fresh bean sprouts, lime, crushed peanuts, and chili flakes on the side.
