How to Make It
Combine peanuts, granulated sugar, and 2 tablespoons water in a small saucepan. Cook over medium, stirring often, until peanuts are lightly toasted and golden and syrup is bubbly, very thick, and almost completely evaporated, 5 to 7 minutes. Immediately spread peanut mixture in an even layer on a parchment paper–lined baking sheet. Let cool completely, about 30 minutes. Break apart to separate peanuts.
Combine all dressing ingredients in a small saucepan. Cook over medium, stirring occasionally, just until sugar is dissolved, 2 to 3 minutes. Remove from heat, and let cool completely, about 30 minutes.
Heat 1 1/2 inches of oil in a Dutch oven over medium to 300°F. Season onion slices with salt; toss with cornstarch, shaking off excess. Fry onions in hot oil in 2 batches, stirring occasionally, until lightly browned and crisp, 3 to 4 minutes. Transfer to a baking sheet lined with paper towels to drain. Season with salt to taste. Let cool at least 5 minutes or up to 1 hour.
Toss together green cabbage, red cabbage, basil, mint, cilantro, candied peanuts, and half of the fried onions in a large bowl. Add dressing, and toss to coat. Top with remaining fried onions; garnish with additional herbs. Serve with lime wedges.
Find palm sugar, tamarind concentrate, and ground dried Thai chile at your local Asian market or online.