To eat surstromming, the bloated, bluish-white, little headless fish is slit in the belly and the roe removed. None but the brave eat the roe. The splayed fish is mashed hard on the spine with a fork and turned over. The bones can then be easily lifted off. The wine-colored fermented flesh inside is then placed on a buttered krisp, a Swedish cracker, with mashed potatoes. Swedes use a small long yellow fingerling potato with a floury texture--a breed designed to survive the northern winter. In the north of Sweden, onions are added, but in the south this is regarded as an unnecessary distraction. Once