In a medium mixing bowl, whisk together the whole wheat flour, all purpose flour, salt, and baking powder until combined.
Grate the very cold butter into the bowl. Use the tips of your finger to gently rub the butter into the dry ingredients until you have pea-sized chunks. Place the dry ingredients into the fridge to keep cold while you prep the wet ingredients.
In a small bowl, whisk together the buttermilk, egg, vanilla extract, and honey until the honey has completely dissolved.
Remove the dry ingredients from the fridge and fold in the dried cranberries and chopped walnuts until evenly distributed. Pour in the wet ingredients and use a spatula to fold until the dough comes together and all the flour is incorporated. The dough should be fairly sticky and moist.
Line a baking tray with parchment paper. Transfer the dough onto a floured countertop. Sprinkle the top with flour and use your hands to gently pat into a 6 inch by 6 inch square. Use a knife or bench scraper to divide into 9 equal squares, each about 2 inches wide.
Place the slices on the prepared baking tray about 1 – 2 inches apart. Place the tray in the fridge to chill for 15 minutes.
While the scones are chilling, preheat the oven to 400°F
Once the scones have chilled, brush the tops with milk and sprinkle with coarse sugar. Place in the middle rack and bake for 17 - 18 minutes until the edges just begin to brown.
Remove from the oven and enjoy! Store leftover scones in airtight containers at room temperature.