Preheat the oven to 350 degrees F.
Using mixer, in mixing bowl, mix together the the flour, sugar, cocoa, baking soda, baking powder, and salt.
In another bowl, whisk together the the milk, oil, eggs, and vanilla together and . Slowly add the wet ingredients to the dry ingredients.
With mixer still on low, add the coffee and stir just to combine, scraping the bottom of the bowl with a rubber spatula. Optional: add mini chocolate chips if desired.
Right before you pour the batter into the bundts, use Baker's Joy or or use melted or solid shortening, coating your pan well with a brush or paper towel, making sure to get in all the nooks and crannies center tube of the pans, then dust with cocoa powder or flour. Then flip the pan over and tap out the excess flour to prevent a buildup of grease and flour on the finished cakes. (Greasing your cake pans too early allows the oil to slide down the inside of the pan and pool in the bottom.)
Because the batter is on the runnier side, I recommend dividing up the batter into large piping bags, making it easier to get the batter into the mini pans.If you don't want to go the piping bag route, you can always use a spoon or a glass measuring cup. Have paper towel available to wipe away any excess batter that gets on the sides. Pipe or spoon/pour the batter into the prepared pan at 2/3rds full and bake for 22 to 26 minutes, until a cake tester comes out clean. Let the cakes cool in the pan for 10 minutes and then remove and cool the rest of the way on a cooling rack.After removing from the oven, place the pan on a wire rack and let cool 10 minutes. This allows the cake to become firm enough to remove from the pan without breaking apart. At this point you can carefully slide a table knife or spatula down the sides and center of the pan to release any sticking spots. After the required cooling time (cooling too long in the pan will cause the cake to be damp and stick to the pan), tap the pan firmly a few times and shake it gently to help loosen the cake. Invert the pan onto the rack, lift it off and let the cake continue to cool on the rack.