Preheat your oven to 350ºF.
Put the coffee, cocoa, butter and grapeseed oil in a small saucepan and heat, stirring, until the butter melts. Stir everything together so it is well blended, then take it off the heat and set aside for 10 minutes.
In a large bowl, put the sugar, baking powder, baking soda, salt and flour, and stir it gently with a fork.
After the cocoa mixture has cooled for 10 minutes, add it to the bowl and mix—I used a regular wooden spoon. Residue will cling to the sides of the bowl—scrape it down and keep stirring until everything is evenly mixed.
Next, whisk together the eggs, sour cream and vanilla in a small bowl until it is uniform. Add it to the big bowl and mix again to combine everything nicely.
Prepare your bundt pan now—brush it thoroughly with some melted shortening or coat with a cooking spray. Then immediately pour in the batter.
Bake for 45 to 55 minutes, depending on your oven. This is done when a tester inserted at the center comes out clean. Our oven is rather fast, so for us this was ready at 45 minutes exactly.
Set the pan on a rack and let it cool for 5 minutes. Then gently ease a thin knife around the edges of the pan, to loosen the cake. Be careful! You don’t want to damage the surface of the cake. Then right away, place another rack on top of the pan, the up side of the rack facing down, invert the bundt pan so it is resting face down on the new rack, and let it sit on your counter another 5 minutes. The cake should slide out easily at that point. If not, see Kitchen Notes.
When the cake is completely cool, and not before!, it may be iced.
Make the glaze. Put the sugar, bourbon and butter in a small saucepan. Cook it over low heat, whisking constantly, until the sugar has dissolved and the butter is melted. You will know this is ready when you don’t see any sugar crystals. Ice the cake right away. I found that what worked best with this glaze was to spoon it over the cake rather than spread or pour it on—that gave me the amount of control I wanted. You can also brush it on with a silicone brush.