Preheat your oven to 350 degrees F. Line a 9x13 inch glass pan with parchment paper or foil. Spray with nonstick spray if you use foil.
In a large bowl or stand mixer, beat butter for 1-3 minutes, scraping sides, until light and fluffy.
Add the brown sugar and beat again.
Add molasses, eggs, and vanilla. Beat well, scraping sides.
In a separate bowl whisk together flour, baking powder, baking soda, salt, nutmeg, and cinnamon. Crush 8 candy canes in a food processor. (I like to add the Lightly Dried Ginger to let it get a little more chopped up, but you don't have to.) If you don't have a food processor put them in a ziplock and use a rolling pin. Add the candy cane and the Lightly Dried Ginger to the flour mixture and whisk in.
Stir the dry ingredients into the butter mixture until just combined.
Spread the batter evenly into the prepared pan. Bake at 350 for 27-28 minutes, or until a toothpick comes out clean. Err on the side of under baking, just as you would with brownies.
Remove from the oven and let cool completely. When cool, lift the bars from the pan.
Meanwhile make the frosting. Beat 3/4 cup butter until smooth, 1-3 minutes (depending on how cold your butter is).
Add 1 cup powdered sugar and the vanilla.
Add the remaining powdered sugar, 2 tablespoons milk, and 1/4 teaspoon salt. Beat well. Add more milk or powdered sugar to reach desired consistency. Beat well, scraping the sides and bottom of the bowl.
Spread the frosting over the bars. Sprinkle with 3-4 crushed candy canes right away. You could also stir them straight into the frosting. Then stuff your face.