Brussels Sprout Tacos with Spicy Peanut Butter

Name: Brussels Sprout Tacos with Spicy Peanut Butter
Ingredients: 3 Tbsp. fish sauce; 1 cup unseasoned rice vinegar; ¼ cup sliced scallions; 1 ½ piece ginger, peeled, finely grated; Kosher salt; 2 Tbsp. Aleppo-style pepper or 1 Tbsp. crushed red pepper flakes; ¾ cup unsalted, roasted peanuts plus ¼ cup crushed; 1 lb. brussels sprouts, preferably small ones, trimmed, divided; 1 cup vegetable oil; 8 6 corn tortillas; ¼ cup finely chopped white onion; Sliced avocado, sliced serrano chiles, cilantro leaves with tender stems, flaky sea salt, and lime wedges (for serving)