Combine flour, both sugars, spices and salt in a large bowl. In a separate medium bowl, whisk eggs, oil, sour cream, molasses, ginger and vanilla together. Then whisk the water-baking soda mixture into the egg mixture.
Fold wet ingredients into flour mixture until combined. Spray mini bundt pan with nonstick cooking spray. Pour batter about 2/3 of the way into each mold.
Bake in a preheated oven for 18-22 minutes, until a toothpick inserted in the middle comes out clean. Cool to room temperature before turning out onto a wire rack.
Whisk all of the frosting ingredients together in a small bowl. Pipe or spread over the gingerbread cakes and sprinkle with more confectioner's sugar just before serving.