The Baltic sprat (Sprattus sprattus balticus) is a subspecies of the European sprat (Sprattus sprattus), also known as brisling or skipper. They are up to 12,5 cm long (about 5 inches), small, silvery and herring-like. The sprats are commonly marinated in a mixture of black pepper, allspice (aka Jamaican pepper), cloves, nutmeg, coriander seeds, bay leaves, salt and sugar etc. The result: spiced Baltic sprats aka vürtsikilud, a famous Estonian delicacy.
In any case, I thought it's a good idea to share the "recipe" with you, my dear readers. Although hard-core fans of kiluvõileivad probably filet and pickle their own fresh Baltic sprats, then you can buy rather decent prepared and canned/packed Baltic sprats in the supermarket. I use the Briis brand, made in a nearby Maardu town, so they're almost local :)
Do buy a packet or two next time you're in Estonia, ok! ;) Alternatively, you could try with Swedish "anchovies" (these are actually sprats or Baltic herrings), probably available at IKEA, but these are much sweeter in flavour.
Estonian spiced sprat sandwiches