Preheat the oven to 325ºF degrees. Grease and flour a 9-inch bundt pan with butter or cooking spray and set aside.
Combine the butter, molasses, dark brown sugar and 1/4 cup water in a medium saucepan over medium-low heat. Cook, whisking constantly, until the butter has melted, then pour the mixture into a large bowl and let it cool for 10 minutes.
Once cooled, whisk the eggs and milk into the molasses mixture.
Sift together the flour, cocoa powder, baking soda, salt, ground ginger, cinnamon, allspice and nutmeg into a medium bowl. Gently fold the flour mixture into the molasses mixture, stirring just until combined, and then stir in the chocolate chips. Pour the batter into the prepared pan. (See Notes.) Bake the cake for about 30 minutes, or until a toothpick inserted comes out clean. Allow the cake to cool fully while still in the bundt pan.
Make the glaze by whisking together the sifted confectioners sugar, heavy cream and vanilla extract until smooth.
Once the cake has fully cooled, invert it onto a serving platter, drizzle with the glaze and serve.
Once you've poured the batter into the bundt pan, place the pan on a towel on the counter and tap it to release any air bubbles.
The cake can be made one day in advance, and the flavors will actually develop more fully if you make it ahead of time. The glaze can be prepared one day in advance and stored in an airtight contained in the fridge. When ready to serve, re-whisk the glaze, adding additional heavy cream or water to thin the glaze if necessary.