Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, whisk together the flour, brown sugar, baking powder, ground ginger, cinnamon, nutmeg, allspice, and salt until fully combined.
Add the cold, cubed butter into the flour mixture and use a pastry cutter or your fingers to work the butter into the mixture until it resembles coarse crumbs.
In a separate bowl, whisk together the molasses, heavy cream, and egg until smooth and well combined.
Pour the molasses mixture into the dry ingredients and gently mix everything together until just combined. If using, fold in the chopped crystallized ginger.
Turn the dough onto a lightly floured surface and gently knead it a few times until it comes together. Pat it into a circle about 1-inch thick.
Cut the dough into 8 equal wedges (like a pizza) and place them on the prepared baking sheet, leaving a little space between each scone.
Bake in the preheated oven for 15-18 minutes or until the scones are lightly golden and a toothpick inserted comes out clean.
While the scones are baking, prepare the glaze by mixing the powdered sugar with milk until smooth and drizzle-able. Adjust the milk quantity for desired thickness.
Once the scones are baked, remove them from the oven and let them cool for a few minutes before drizzling the glaze over the top.