In a medium-large pot set over medium heat, melt the oil and butter together and saute the onion for about 5 minutes, until soft but not golden. Add the thyme and bay leaf and cook for another minute. Add the potatoes, corn and stock - make sure there is enough liquid to cover the potatoes - if not, add a little more water until it does.
Bring to a simmer and cook for 10-15 minutes, until the potatoes are tender. Dump in the seafood and stir until it turns opaque - this should only take a couple of minutes. Don't overcook the shrimp, or they will curl up and get tough. Stir in the cream and season with salt and pepper.
Divide among bowls and sprinkle with parlsey or chives.