1. Preheat oven to 375°. Beat butter with an electric mixer at medium speed until creamy. Gradually add sugars, beating well. Beat in eggs.
2. Combine flour and next 5 ingredients; add to butter mixture, beating at low speed until blended. Stir in almonds and crystallized ginger.
3. Divide dough in half. Using floured hands, shape each portion into a log 3 inches wide and 1 inch high. Place on a lightly greased cookie sheet.
4. Bake 25 minutes. Cool 5 minutes on cookie sheet; remove to a wire rack, and set aside until cool to the touch. Reduce oven temperature to 325°.
5. Cut each log crosswise into 1/2-inch slices with a serrated knife. Place slices on ungreased cookie sheets.
6. Bake 7 minutes; turn cookies over, and bake 7 more minutes. Cool completely on wire racks.
7. Dip ends of biscotti in melted white chocolate. Place biscotti on wax paper until chocolate hardens.