Som Tum is a popular Thai salad that's made with crisp green papaya, tomatoes, lime juice, fish sauce, and pounded together in a large mortar and pestle.
Peel the papaya and cut in half length wise and scoop out the seeds. Do a quick soak in ice water to ensure the papaya is cold. Shred the papaya with a mandolin or peeler. You want to end up with fine julienne shreds.
Begin pounding until papaya is evenly coated with sauce and tomatoes have been slightly smashed. If using peanuts, you can add them last.
Use a food processor or finely chop the garlic and chili peppers. Then in a small bowl mix the fish sauce, lime juice, and sugar with the garlic chili paste. Pour the sauce over the shredded papaya, tomatoes, green beans, dried shrimp, peanuts, and toss to coat everything.
Dried shrimp can be found at Asian markets. It is usually packaged in the refrigerated section. If you can't find dried shrimp, then you can boil some regular shrimp and place those on top for garnish.