Cream butter and sugar until light. Add flour and salt. Chill slightly and roll 0 cm thick between wax paper sheets. Roll only a small amount of dough at a time. Using a 6 cm cookie cutter, cut cookies. Cut center out of half of cookies (I use my thimble to cut centers). Bake all cookies on ungreased sheets at 200ºC for 8-10 minutes or less, until very lightly browned. Cool on wire racks. Spread whole cookies with preserves, piled higher in center. Top with cookie ring. Sprinkle with 4x sugar. Store in tin box between layers of wax paper.