Prepare the chorizo oil. Finely mince the chorizo into ⅛-inch cubes and sweat on the stove top over low heat in olive oil [½ cup]. Use a wooden spoon to press down on the chorizo until the olive oil starts to turn a brilliant red color, about 10 minutes. The complex flavor of the chorizo gives the oil fantastic flavor. Remove the crispy chorizo from the oil and set both aside in separate containers; small ramekins work well.
Prepare the garlic butter. In a small pan, melt one stick sweet cream butter and simmer with garlic for 3 minutes over low heat. Pull from the heat and allow to cool to room temperature.
Preheat oven or grill to 400 degrees.
Shuck and loosen oysters in shell.
Arrange oysters in a cast iron baking dish filled halfway with coarse rock salt (a foil-lined baking sheet also functions nicely). The salt helps keep the oysters level and prevents the bottom of the shells from burning. Pour 1 teaspoon of garlic butter over each oyster and add a pinch of fresh oregano. Roast for approximately 8 minutes. Time will vary based on the size of the oysters.
Pull from the oven, drizzle each oyster with 1/2 teaspoon of chorizo oil, then sprinkle with sliced scallions and roast another 3 minutes.
Serve immediately with a small fork.