Mix flour, spices, baking soda, salt in medium bowl. Set aside.
Beat butter, brown sugar 5 minutes on medium speed, until light and fluffy.
Add eggs, mashed yams, vanilla, rum extract, maple syrup, beat another 3 minutes.
Reduce speed to low, add slowly flour mixture, and stir until incorporated.
Add walnuts and dates. Stir to just blend.
Create dough round, divide in half, cover with plastic wrap, chill at least 5 hours.
Preheat oven to 325 F. Line large baking pan with parchment paper.
Roll out dough on floured work surface, 1/4 inch thick. Cut out circles, place on baking sheet.
Bake 10 minutes, rotating once in between. Place on rack in pan for 10 minutes then transfer to cool.
To make frosting, beat butter, cream cheese, extract and zest about 6 minutes on medium speed. Pipe on cooled cookies. Garnish with chopped walnuts