In a small pan over low heat, toast the peppercorns until fragrant, about 5 minutes. Coarsely grind and set aside.
Trim cod of any pin bones or bits of skin and cut into 1-inch cubes. Lightly salt the cubes all over and set aside on paper towels to drain. Rinse scallops very lightly under cold water. Cut into half-moons and set aside on paper towels to drain. Keep seafood refrigerated until ready to use.
In a large pot, melt butter over medium-high heat. When the butter is just sizzling, add onion and potatoes and cook, stirring, until the onions start to melt and the potatoes are gold at the edges, about 5 minutes.
Meanwhile, if using bacon, cook the strips in a hot skillet over medium-low heat, stirring occasionally, until nicely browned, about 5 minutes. Set aside on paper towels to drain.
Add stock, thyme and toasted peppercorns to pot and bring to a simmer. Reduce the heat and simmer for 3 to 5 minutes. The potatoes should not be cooked through.
Stir in cream and heat through over low heat. Taste and adjust the seasonings with salt and pepper.
Just before serving, with the chowder simmering over low heat, stir in seafood and simmer until potatoes are soft and seafood is just cooked through, about 5 minutes. Stir in the bacon.
Ladle the chowder into bowls. You want each serving to be around 2 parts broth to 1 part chunky goodness. Use your fingers to crush the nori into powdery bits, if using, and sprinkle over the top of each serving. Place about 1 teaspoon chives in the center of each bowl and serve immediately.