Preheat your oven to 375 degrees. Brew the coffee. While the coffee is brewing, spray your bundt pan with non-stick cooking spray and then dust with cocoa powder (for extra insurance if needed). Do this well to ensure the mini bundt cakes come out of the bundt pan. Knock out any excess powder.
In a microwave safe bowl, melt the butter for 20 seconds. Mix with the coffee and cocoa powder. Stir with a wire whisk. Once everything is combined, add the sugar and whisk until it has dissolved. Transfer the mixture to a large bowl and set aside to cool for about 5 minutes.
In another medium-sized bowl, combine the flour, baking soda, and salt. And lastly, in a separate small bowl, whisk together the egg and vanilla.
Whisk the egg mixture into the chocolate mixture. Slowly add the flour mixture and continue to mix. Once all of the ingredients have been combined you are left with a batter with the consistency of a slightly thick soup.
Pour the batter into the mini wells of the bundt pan and bake for about 20-25 minutes or until a toothpick inserted comes out clean.
Remove the bundt pan from the oven and let cool for at least 20 minutes. Once cooled, gently run a butter knife or fork around the sides of each cake to gently loosen from the pan. You can either remove with the knife or fork or place a wire rack on top of the bundt pan and flip it to release and catch the mini bundt cakes. Let cool on a wire rack.
Melt the butter in a saucepan over medium heat. Add the brown sugar and the evaporated milk; allow to cook for 2 minutes.
Remove from the heat. Add the vanilla and powdered sugar; stir with a whisk until smooth. Let cool slightly before drizzling on your mini bundt cakes. Sprinkle on some maldon sea salt and serve.