Icebox Cookies

Cream butter and sugars together in a bowl. Add almond extract and egg, mixing thoroughly. In another bowl, toss cream of tartar, salt, and nutmeg with flour. Add flour mixture to batter and beat until blended. Fold in slivered almonds. Turn dough out onto a large sheet of lightly floured waxed paper. Dust hands with flour and shape dough into a roll about 11 inches long and 1 1/2 inches in diameter. Wrap roll in waxed paper and refrigerate at least 4 to 6 hours, or until firm throughout. The dough may stay in the fridge up to 10 days; after that, it should be frozen. When ready to bake a batch, preheat oven to 400 degrees. Cut 1/4-inch-thick slices of dough to make as many cookies as you'd like to eat. Arrange rounds with an inch of space between them on a cookie sheet lined with parchment. Bake 8 minutes or until cookies are golden brown around the edges. Transfer to wire racks to cool, and garnish with extra sugar (if using).