Preheat the oven to 350°F, and line two baking sheets with parchment paper.
In the bowl of a stand mixer with the paddle attachment on low, beat butter and granulated and brown sugars until fluffy. Mix in molasses, eggs and vanilla. Remove bowl from stand mixer, and set aside.
In a separate large mixing bowl, add flour, baking powder and spices, and combine with a whisk. With mixer on low, slowly add flour mixture into wet mixture.
On prepared baking sheets, form dough into 2 loaves, and sprinkle coarse sugar over top. Transfer baking sheets to oven to bake for 50 minutes. Turn oven off once bread is finished baking.
Remove bread from oven and allow to slightly cool to the touch; while still on baking sheets, use a knife to cut each loaf into long slices. Place baking sheets back into oven, and let rest for 25 minutes or until dry.
Icing
In a large mixing bowl, combine all ingredients. Dip mandelbrot into icing, or drizzle on top. Place onto cooling racks to dry. Serve.
Notes
- Biscotti: Very similar in baking techniques and texture to biscotti if you've ever baked that. The drying in the oven process is very necessary to get that crunch.