Finely chop white chocolate. In a pot, heat eggnog over medium heat while stirring generously, making sure it doesn’t burn. Remove from heat, add chopped chocolate and let rest for approx. 5 min., then stir until chocolate has dissolved. Refrigerate for overnight or at least 2 hrs., until thickened.
In a large bowl, mix flour, starch, baking soda, salt, ground cloves, ground ginger, cinnamon and ground anise. Set aside. In another large bowl, beat some of the butter with sugar, and cane sugar until white and frothy in texture. Stir in the molasses and egg, and mix until fully combined. Then, add flour mixture and mix until a smooth dough forms. Cover and refrigerate for approx. 60 min.
Preheat oven to 190°C/375°F and line a baking sheet with parchment paper, if needed. Using a teaspoon, scoop dough into equal-sized small balls. Roll in cinnamon sugar and transfer to baking sheet. Bake for approx. 8 – 10 min., until golden brown. Allow cookies to cool completely.
In a large bowl, beat butter until smooth, add the eggnog-white chocolate mixture and beat until fluffy. Spread the buttercream onto the cookies and decorate with sprinkles, if desired. Enjoy!