Fill a medium fry pan with about 1 inch of water and bring to a simmer. Add peppercorns, bay leaf, 1 lemon wedge and cod and simmer until fish flakes easily with a fork, 6-8 minutes. Transfer cod to a plate and set aside. Discard the water, peppercorns, bay leaf and lemon wedge.
In the same fry pan, heat butter over medium-high heat. Add onion, celery and garlic and cook, stirring occasionally, until tender, about 5 minutes. Transfer to a large bowl and let cool to room temperature.
Add eggs, 1½ tablespoons mayonnaise and next seven ingredients (Dijon mustard through parsley) to bowl with onion, celery and garlic; stir to combine.
Flake prepared cod and add to bowl; stir gently to combine. Form mixture into 8 patties (about ½ cup each) and transfer to a baking sheet. Cover with plastic wrap and chill in the refrigerator for at least 30 minutes.
Smear both sides of cod cakes with remaining 1½ tablespoons mayonnaise.
Heat canola oil in a fry pan over high heat. Add cod cakes to pan and cook for 3-4 minutes on each side until lightly browned. Serve with tartar sauce and remaining lemon wedges.
Make the tartar sauce:
In a small bowl, combine all the sauce ingredients.
Recipe by Two of a Kind at http://www.twoofakindcooks.com/cod-cakes-with-tartar-sauce/