1 onion, chopped
1 potato, diced
1 cup coarsely chopped broccoli
1 cup water
1/2 cup frozen corn
1/4 cup butter
1/4 cup all-purpose flour
3 cups milk
salt and ground black pepper to taste
Cook oysters and reserved liquid in a skillet over medium heat until edges curl, 5 to 10 minutes. Remove skillet from heat. Combine onion, potato, broccoli, water, and corn in a saucepan; bring to a boil. Reduce heat and simmer until vegetables are tender, 10 to 15 minutes. Drain vegetables and reserve liquid. Melt butter in a large pan over medium heat. Stir flour into melted butter until smooth, about 1 minute. Slowly pour reserved vegetable water and milk into butter-flour mixture; cook until thickened, about 5 minutes. Add oysters and vegetables to milk mixture and cook over medium-low heat until heated through, about 5 minutes. Season with salt and pepper.