Add chorizo; saut 3 minutes or until lightly browned.
Add onion; saut 3 minutes or until just tender.
Add sliced garlic; saut 1 minute.
Add sherry; cook 1 1/2 minutes, scraping pan to loosen browned bits. Stir in broth and next 5 ingredients (through chickpeas); stir to combine. Nestle halibut fillets in stew; spoon tomato mixture over fillets. Cover and simmer 5 minutes or until fish flakes easily with a fork or desired degree of doneness.
Place ciabatta slices on a baking sheet. Broil 1 minute or until toasted.
Brush toasts with remaining 1 teaspoon oil; rub toasts with cut sides of halved garlic clove.