Heat oven to 375 degrees F. Coat 3 mini muffin pans (12 cups in each) with nonstick cooking spray.
Mix flour, baking powder, baking soda, cinnamon, nutmeg and salt in large bowl.
Beat butter and sugar in second large bowl until smooth, about 3 minutes. Add eggs; beat 1 minute. Add sweet potatoes and milk; beat until combined. Mixture may look somewhat curdled at this point.
Make well in center of flour mixture. Add sweet potato mixture to well; stir with wooden spoon until flour mixture is just moistened. Fold in raisins and pecans. Spoon into muffin pan cups, dividing equally.
Bake in 375 degree F oven about 18 minutes or until wooden pick inserted in centers of muffins comes out with just a few moist crumbs clinging. Turn muffins out onto wire rack and cool.
Beat together cream cheese, sugar, orange rind and juice, and vanilla in medium-size bowl until smooth.
Spread frosting over cooled muffins. Garnish with pecans and orange rind, if desired. Makes about 3 dozen mini muffins.