Choose a pot of simmering water that can act as the base for a double boiler, and bring the water to a lively simmer.

In the pot you will use for the sauce, combine the oil and butter over medium-low heat. Heat until the butter is fully melted and just begins to foam.

Add the garlic and saute very briefly, without letting it take on any color.

Set the sauce pot over the simmering water. Add anchovies and cook, stirring frequently and mashing with the back of a wooden spoon until they dissolve into a paste. Add salt, stir, and bring to the table over a warming apparatus.