Heat a large sauté pan over medium heat. Add 1 teaspoon oil to pan; swirl to coat. Add chorizo; sauté 3 minutes or until lightly browned. Add onion; sauté 3 minutes or until just tender. Add sliced garlic; sauté 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. Serve toasts with stew.