Per anchovy fillet that you are trying to use up, use 1 tablespoon of butter (you can use 1 ½ or 2 fillets per tablespoon of butter if you are a real anchovy lover), a squish of lemon juice and a light shake of pepper.
Soften the butter and mash all the ingredients together. Roll the butter up in a log shape wrapped in wax paper, and freeze inside tin foil or a freezer bag. To use, cut off slices as you need it. You can keep this in the freezer up to 3 months.
Notes
It's great to have in the freezer. You can toss hot pasta in dollops of it for a quick, creamy pasta, or use it as you would Maître d'Hôtel Butter to garnish meats or fish hot off the grill or out of the frying pan.