Melt butter in pot. Add onion and saute. Add the potatoes and garlic until the potatoes have softened slightly.

Add chicken stock, tomatoes, and carrots. Bring to boil, then reduce heat and simmer about 10 mins.

Add the milk, cream, season to taste, then stir in halibut. Simmer halibut until fish is flaky, about 10 mins. Stir in cheese if you want.