Preheat oven to 325. Line a baking pan (10X13 pyrex) with parchment paper.
In a large saucepan or dutch oven, melt the butter with the sugars, syrup, molasses, cloves, cinnamon and ginger.
Dissolve baking soda in water.
Take the saucepan off heat and add eggs, milk and soda/water mixture. Stir in flour and cocoa, reserving 2 T or so of the flour. Toss the chocolate chips in the reserved flour, then fold in chocolate chips.
Bake about 45 min until risen and firm. The middle should still be a little damp under the set top, and will sink a little. Cool in the pan.
While the cake is cooling, melt the butter, cocoa and ginger ale for the frosting. Whisk in the powdered sugar. Remove the cake from the pan, fold down the paper, and pour frosting over the cake. Let frosting set slightly, and cut into large slabs.