2 tablespoons finely chopped fresh rosemary
12 salted anchovy fillets, prepared (see here)
juice of 2 lemons
150 ml (5 fl oz) extra virgin olive oil
Crush the rosemary in a mortar, add the anchovies and pound to a paste. Slowly add the lemon juice, stirring to blend. Finally add the olive oil a drop at a time. When about half has been added, pour in the remainder in a thin, steady stream, stirring continuously. Alternatively, you can use a food processor although this method produces a thicker sauce. Put the rosemary in and chop very finely, then add the anchovy and chop to a thick, fine paste. Pour the oil in slowly. Finally, add the lemon juice.