Line a plate with paper towels. Cook the bacon in a large, heavy pot or Dutch oven over medium heat until crispy, about 7 minutes. Remove the bacon with a slotted spoon and place on the paper towel-lined plate.
Leave 1 tablespoon of fat in the pan and pour off the rest. Return the pot to medium heat. Add the butter and allow it to melt, then add the onions and leeks and sauté for 5 minutes until they start to soften. Add the wine and stir to release any browned bits from the bottom of the pan. Add the clam juice or broth, milk, potatoes, 1/2 teaspoon salt, and some pepper. Bring to a gentle simmer, then partially cover the pot, adjust the heat so it stays at a simmer, and cook until the potatoes are almost tender, about 10 minutes.
Add the cream and salmon and return to just barely a simmer. Stir carefully so the salmon doesn’t totally fall apart as it cooks; you want some nice flaky chunks. Simmer for a few minutes until the salmon turns opaque. As soon as the salmon starts to become cooked, add the peas, scallions, and 3 tablespoons of fresh dill. Season with salt and pepper. Stir for another 2 minutes until the salmon and potatoes are fully cooked through.
Serve the chowder in bowls, sprinkled with a bit of extra chopped fresh dill.
Notes
Freezing chowder is a little tricky — the dairy in the soup may separate when you defrost and reheat it. The flavor will still be good, but it might look grainy. Still, reheated leftover frozen chowder is better than no chowder.