How to Make It
Place potatoes in a small saucepan; cover with cold water by 1 inch. Place pan over medium-high; bring to a simmer and cook 1 minute or until potatoes are not quite fully tender. Drain well; sprinkle with 1/4 teaspoon salt and set aside.
Heat oil in a large skillet over medium-high. Add fennel, onion, garlic, tarragon, 1/2 teaspoon salt, and 1/4 teaspoon pepper; sauté 4 minutes or until vegetables are tender. Add wine, stock, and lemon slices; bring to a simmer. Sprinkle cod with remaining 1/2 teaspoon salt and remaining 1/4 teaspoon pepper. Add potatoes and cod, nestling cod into sauce; cover, reduce heat, and simmer 5 minutes or until fish is done. Divide potato mixture evenly among 6 bowls; top each serving with 1 fish fillet. Serve with lemon wedges, if desired.