Preheat the oven to 350°F, and generously butter and flour a 10-inch Bundt pan.

In a large bowl, combine the sugar, ginger and orange zest. Use the back of a spoon, or even your fingers, to blend them together.

Add the butter, and beat until light in texture.

Add the eggs one at a time, beating continuously.

In a second bowl, measure about 1/3 cup of the orange juice (you can use the rest for something else), yogurt, and vanilla, and blend together.

In a third bowl, add the flour, baking powder, baking soda, and salt. Sift to blend together.

Add about 1/3 of the yogurt mixture to the egg mixture, and fold into the batter.

Now, add 1/3 of the flour mixture, and blend it in.

Repeat until the batter is fully incorporated.

Add the chocolate chunks last.

Bake in the oven for about 45 minutes, up to 1 hour. A clean knife inserted in the center should come out dry (other than melted chocolate!)

Create a double boiler by placing a heat-proof bowl or smaller pot inside a larger pot about 2/3 full of water.

Melt the chocolate, and stir in the heavy cream and instant coffee until well blended. It should be smooth in texture, and warm, but not bubbling hot.

Drizzle over the top of the cake.