In a large bowl, combine chicken, chorizo, bread crumbs, Worcestershire sauce, 1 teaspoon kosher salt, blue cheese and parsley. Form into 6 equal-sized patties. Place on a plate; refrigerate 30 minutes.
Meanwhile, in a large skillet, over medium high heat, melt butter. Add onions, garlic and 1/4 teaspoon salt. Cook, stirring, until onions begin to soften and brown around edges, about 4 to 5 minutes. Add orange juice and balsamic vinegar. Lower heat; simmer liquid until reduced by about half. Stir in raspberries, raspberry preserves, tarragon and crushed red pepper flakes. Cook 4 to 6 minutes, or until slightly thickened. Season with kosher salt to taste. Set aside.
Preheat an outdoor grill or grill pan on stovetop to medium-high heat. Spray grill (or grill pan) with nonstick cooking spray. Grill patties, flipping once, 4 to 5 minutes per side or until chicken is cooked through and is no longer pink.
Spread mayonnaise on cut side of each bottom bun. Top each bottom bun with greens, dividing equally. Top each with a chicken patty and raspberry-onion jam. Sprinkle with additional blue cheese, as desired. Close with top buns.