In a large bowl, blend butter, maple syrup and vanilla extract with electric mixer until smooth. Add buckwheat flour, salt and cinnamon to the bowl and mix until well combined. Next, fold in cranberries, ginger and walnuts. Scoop dough out onto a large piece of plastic wrap. Press and smooth the dough into a 12-inch long log tightly wrapped with plastic. Place wrapped dough in refrigerator to chill for at least an hour and up to a day.
When ready to bake, preheat oven to 350ºF. Line a baking sheet with parchment paper.
Unwrap chilled dough and place on a piece of wax paper that has been sprinkled with turbinado sugar. User paper to gently press sugar into surface of dough, to form a sugary crust. Slice log into 1/4-inch thick slices, and place rounds 1-inch apart on a lined baking sheet. Bake in a 350°F oven for 12 to 15 minutes or until edges brown slightly. Remove from oven and let cool for 2-3 minutes on baking sheet, then transfer to a wire rack to cool completely. Cookies can be kept in an airtight container for up to 5 days.