1. In a large pot, melt the butter over medium heat. Add the chopped onion and minced garlic, and sauté until the onion is translucent.
2. Add the diced potatoes and fish stock to the pot. Bring to a boil, then reduce the heat and simmer until the potatoes are tender, about 10-15 minutes.
3. Stir in the heavy cream and corn kernels. Cook for another 5 minutes.
4. Add the mixed seafood to the pot. Cook until the seafood is just cooked through, about 5 minutes. Season with salt and pepper to taste.
5. Garnish with fresh parsley before serving. Enjoy your seafood chowder!