Dice the Yukon Gold potatoes and yellow onion into small, uniform pieces. Place the potatoes in a bowl of cold water to prevent browning.

Melt half of the unsalted butter in a large soup pot over medium-low heat. Add the diced onions and bay leaf, cooking for about 5-7 minutes until onions are translucent.

Add the drained potatoes and enough cold water to cover them. Bring to a gentle boil and cook until the potatoes are fork-tender, about 10 minutes.

Gently lay the haddock or cod fillets atop the potatoes, pour in evaporated milk and half-and-half evenly, and cover. Let simmer on low heat for about 15 minutes.

Check that the fish flakes easily and the potatoes are tender. Remove the bay leaf, add remaining butter, and season with kosher salt and pepper. Stir gently.

Ladle the chowder into warm bowls, garnish with chives, and serve with oyster crackers or warm buttermilk biscuits.