Put the oil in a pan with the garlic and anchovies and cook over low heat, stirring, until you have a melted, muddy mess. Everything should begin to meld together. Whisk in 6 tablespoons of butter, and as soon as it has melted, remove from the heat and give a few more beats of your whisk so that everything is creamy and amalgamated. Taste, and if you feel you want this as a dipping sauce - which is meant to be pungent but not acrid. If you want the sauce a little more mellow, whisk in the remaining 2 tablespoons of butter. Pour into a dish that, ideally, fits over a flame so that it does not get cold at the table.