In a large heavy pot, melt the butter and olive oil over medium heat. Add the chopped onions and saut? until translucent and softened, about 5 minutes.

Add 2 cups of water, thyme, bay leaves, kosher salt, and black pepper to the pot. Bring to a boil.

Add the cod to the pot, placing the pieces flat in one layer. If necessary, add more water until it comes up to the top of the fish. Cover and cook on low for 4-5 minutes until the fish flakes apart.

Remove the fish to a plate and cool in the fridge or freezer. Once cool, gently flake the fish apart.

Add the clam juice and cubed potatoes to the pot. Bring to a boil, cover, and simmer on low for about 15 minutes until the potatoes are soft.

While the potatoes are cooking, scald the milk in a small saucepan with the quartered onion layers. Boil, then reduce to low and simmer uncovered for 5-7 minutes.

Strain the scalded milk into the pot and discard the solids. Add the flaked fish, chives, and nutmeg to the pot.

Bring the chowder back to a simmer. Turn off the heat and stir in the heavy cream gently.

Serve and garnish with butter, nutmeg, chives, and black pepper if desired.