1 1/4  pounds        red-skinned sweet potatoes (yams)
   4      large         eggs
   1 1/2  cups          buttermilk
   2 1/3  cups          yellow cornmeal
   1      cup           all purpose flour
   1/2  cup           sugar
   1      tablespoon    baking powder
   1 1/2  teaspoons     salt   
1/2  teaspoon      baking soda
     1/4  teaspoon      ground ginger
   1/2  cup           chilled unsalted butter  (1 stick) , cut in 1/2 " pieces
Preheat oven to 375?F. 
Butter 9 x 9 x 2-inch baking pan. 
Pierce sweet potatoes in several places. 
Microwave on high until tender, turning once, about 12 minutes. 
Cut open and cool. 
Mash enough potatoes to yield 1 cup packed 
(reserve remaining potatoes for another use). 
Place 1 cup mashed potatoes in large bowl. 
Whisk in eggs and buttermilk. Blend 
Place cornmeal and next 6 ingredients in food processor. 
Add butter and blend until mixture resembles coarse meal. 
Add to egg mixture. Stir just until blended.  
Transfer to prepared pan.
Bake corn bread until deep golden on top and tester inserted into center comes out clean,  about 45 minutes. 
Cool in pan on rack. (Can be made ahead. Cover and let stand at room temperature up to 2 days or freeze up to 2 weeks. Thaw at  room temperature.
Serving size 10