1. In large saucepan, heat oil over medium heat. Add onions and garlic; cook 3 minutes. Add potatoes; sauté 3 minutes. Add broth; simmer, covered, 15 minutes or until potatoes are tender.
2. Add watercress to pan; cook 3 minutes, until wilted. In batches, purée soup in blender; return to pan. Whisk in 1/4 cup yogurt, salt, and pepper; reheat gently (do not boil). Serve with remaining 3 TBSP yogurt and almonds.