In a large bowl, combine the chocolate chips, cocoa powder and espresso powder. Add boiling water and whisk until the chocolate is melted and the mixture is smooth. Let it cool for 20 minutes.

Meanwhile, preheat the oven to 350°F (180°C).

Add the brown sugar, baking soda, salt, eggs, sour cream, butter and vanilla to the cocoa mixture. Using an electric mixer on high speed, beat for 2 minutes, until it is blended and fluffy. Add the flour and beat on medium speed for 1 minute. Scrape the sides and bottom of the bowl with a spatula. Beat again, this time on high speed for 1 minute.

Spray a 10-inch (25 cm) Bundt pan with nonstick baking spray and dust with flour. Spread the batter evenly in the prepared pan.

Bake in a preheated oven for about 60 minutes or until a piece of uncooked spaghetti inserted in the center comes out with a few moist crumbs attached. Let cool in pan on a wire rack for 10 minutes, then invert the cake onto the rack to cool completely. Spoon the glaze over top of the cooled cake (if you are glazing it), letting it drizzle down the sides.

Store the glazed cake at room temperature in a cake keeper, or loosely wrapped in foil or plastic wrap, for up to 3 days. Alternatively, wrap the cooled, unglazed cake in plastic wrap, then foil, completely enclosing the cake, and freeze for up to 6 months. Let the cake thaw at room temperature for 4 to 6 hours before serving.

If desired you can serve pieces of this cake glazed or drizzled with chocolate sauce.