For tomato-sherry vinaigrette, combine ingredients in a large bowl and season to taste.
Brush bread with oil and char-grill over high heat, turning once, until golden and charred on both sides (2-4 minutes). Rub with cut sides of garlic and keep warm.
Grill mussels and chorizo on a barbecue, turning once, removing mussels as they open, until chorizo is golden and cooked through and all mussels are open (6-8 minutes for chorizo; 8-10 minutes for mussels). Transfer to tomato-sherry vinaigrette bowl, toss to combine and season to taste. Spoon onto grilled bread, drizzle with juices and serve scattered with parsley.