1.Heat large saucepan; cook chorizo, turning, until crisp. Remove from pan. Cook chicken, in batches, until browned all over. Remove from pan.
2.Add onion, celery, capsicum, fennel and garlic to pan; cook, stirring, until softened. Add saffron, paprika, paste and the water; bring to the boil. Return chicken and chorizo to pan. Reduce heat, simmer, uncovered, about 15 minutes or until chicken is cooked through and sauce thickens. Stir in olives. Transfer to 1.5-litre (6-cup) ovenproof dish.
3.Meanwhile, preheat oven to 220°C/425°F. Arrange potato slices, slightly overlapping, over chicken mixture. Bake, uncovered, about 45 minutes or until potatoes are tender.