Preparation

• In a medium bowl, stir together the vinegar, sugar and 1/2 tsp. salt until the sugar and salt dissolve. Add the sliced chiles and let sit for at least 30 minutes.
• Heat a 12-inch cast-iron skillet over medium-high heat until beads of water dance across the surface, about 2 minutes. Add the duck legs, skin side down, and cook until the skin is browned and crisp, 3 to 4 minutes. Flip and cook until the legs are completely heated through, 3 to 4 minutes more.
• Transfer the legs to a cutting board and rest until cool enough to handle. Pour off all but 1 Tbs. of the duck fat from the skillet. Add the cabbage to the skillet and reduce the heat to medium. Using tongs, toss the cabbage until it is wilted but still a little crunchy, about 4 minutes. Season to taste with salt and pepper. Transfer to a medium bowl and set aside to cool.
• Once the meat is cool enough to handle, strip the meat from the bones and shred.
• Divide the rice among the lettuce leaves. Top with the cabbage, chiles, pistachios, and duck. Sprinkle with the tarragon, drizzle with some of the pickling liquid, and serve.