In large saucepan, cook bacon over medium-high heat until crispy, 5 minutes. With slotted spoon, remove bacon; reserve for optional garnish.
To drippings in pot, add onion, celery and garlic; cook over medium heat, stirring, until vegetables are very tender, 10 minutes. Add wine; cook until almost dry, about 3 minutes. Pour in clam juice and fish bouillon; bring to boiling. Add diced potatoes; cook 5 minutes. Whisk in mashed potatoes. Bring to simmering.
Add fish to chowder; simmer until fish is cooked through, 2 to 3 minutes. Stir in parsley, chives, pepper and bacon pieces if desired.
