Brown sugar (packed)
Half and half
Preheat oven to 350 F (175 C). Grease several baking sheets with butter and dust with flour. In a large bowl, beat butter with brown sugar until very creamy. Beat in egg, sour cream and milk. Sift flour, baking powder, salt and allspice into bowl; mix well. Stir in raisins. Drop heaping teaspoonfuls of mixture onto prepared baking sheets, spacing well apart.
Using a fork dipped in cold water, flatten each teaspoonful slightly. Bake about 15 minutes or until lightly browned. Meanwhile, prepare glaze. In a small bowl, beat together powdered sugar, half and half and vanilla until smooth. As soon as the cookies come out of the oven, brush a thin layer of glaze over each one. Place on a wire rack to cool. Source: "The Book of Cookies" by Pat Alburey, HP Books.