Although most of the cured herrings served at the Christmas table come essentially ready to serve, one can also buy whole fillets of herrings preserved in salt and sugar that can be further prepared in various ways. These strongly flavoured fillets are the basis of many dishes, and here I provide the recipe for the preparation Riitta and I made this year. As with many such recipes, quantities are not strict. This recipe calls for soured cream, which is readily available here and convenient as we use it in several other Christmas recipes. Smetana would be more commonly used in Finland. Use either, or, indeed, crème fraîche, according to preference.
The herrings might be a little difficult to find in this country, unless one has Finnish connections, although a certain well known Swedish store often has something suitable.