Begin by preheating the oven to 350°F/175C (155C Fan) and prepare your Bundt pan by greasing and flouring thoroughly.
In a large mixing bowl, beat together the butter and sugars until creamed and light.
1 cup unsalted butter, 1 cup superfine granulated sugar, ½ cup light brown sugar
Add the molasses and beat to incorporate. Then add the eggs one at a time, beating after each addition.
½ cup molasses, 4 eggs
Add the sour cream and beat to combine.
1¼ cup sour cream
Sift the dry ingredients - the flour, ginger, cinnamon, baking soda, baking powder and salt - into the mixing bowl and stir together with a spatula until just combined.
3 cups all purpose flour, 3 teaspoon ground ginger, 1 teaspoon ground cinnamon, ½ teaspoon baking soda, ½ teaspoon baking powder, 1 teaspoon salt
Spoon the batter into the prepared Bundt pan and spread evenly.
Place into the center of the preheated oven and bake for about an hour. Check regularly after about 55 minutes and remove once a toothpick inserted into the thickest part of the cake comes out clean.
Allow to cool in the pan for about 15 minutes before turning out onto a wire rack to continue cooling.