Place anchovy butter slices in a single layer on a parchment paper–lined baking sheet. Cover and freeze until very firm, at least 2 hours. Transfer frozen butter slices to an airtight freezer-proof container until ready to use. Butter slices may be refrigerated up to 5 days and frozen up to 6 months.
This recipe can be served with warm bread, spread on top of roasted oysters, or used to season warm meats or vegetables.