1. Prepare the ingredients by draining the oyster juice and setting it aside. Finely chop the onions and garlic, and measure out the milk and optional seasonings.
2. In a large saucepan, melt butter over medium to medium-low heat. Add the chopped onions and garlic, cooking until they are tender and aromatic. Stir occasionally to avoid burning.
3. Pour the reserved oyster juice into the saucepan with the sautéed onions and garlic. Cook the mixture until the juice is reduced or heated through to enhance flavor.
4. Gradually add whole milk or half-and-half to the saucepan while keeping the heat at medium-low. Stir gently and heat until steaming, avoiding boiling to prevent curdling. Add salt, black pepper, and optional spices like paprika or Worcestershire sauce, as desired.
5. Gently add fresh oysters to the mixture and cook on low heat until the edges of the oysters begin to curl. This process typically takes 2-8 minutes depending on the heat level. Stir occasionally to ensure even cooking.
6. Taste the stew and adjust the seasonings if necessary. Serve hot, garnished with fresh parsley, fennel fronds, or any preferred herbs. Pair with oyster crackers or crusty bread for a wholesome and authentic meal.