In a medium-large pot set over medium heat, melt the oil and butter together and sauté the onion for about 5 minutes, until soft but not golden.
Add the celery, red pepper and dill or thyme and cook for a few more minutes.
Add the potatoes, corn and stock—make sure there is enough liquid to cover the potatoes—bring to a simmer and cook for 15 minutes, or until the potatoes are tender.
Add the salmon (and raw shrimp, if you’re using them), cover and cook until the fish turns opaque— this should only take a minute or two.
Stir in the cream, cooked shrimp if you’re using them, and season with salt and pepper.
Serve hot, sprinkled with extra dill if you have it.