1. Finely chop 1 garlic clove; place in an 11-cup food processor. Add cucumber and next 6 ingredients (through mint). Add 1 tablespoon oil, tarragon, and salt; process 1 minute or until almost smooth. (For smaller food processor bowls, work in 2 batches.) Cover and chill up to 8 hours.
2. Preheat oven to 450°.
3. Smash remaining garlic clove; place in a small bowl with remaining 1 teaspoon oil. Microwave at HIGH for 15 seconds; let stand 5 minutes. Drizzle garlic oil over bread cubes; toss to coat. Place bread on a jelly-roll pan. Bake at 450° for 8 minutes or until browned, turning once. Stir chile into chilled soup. Add up to 1/2 cup water to thin soup, if desired. Ladle soup into bowls; top with croutons.