Preheat the oven to 375 degrees.
In a large bowl add your wet ingredients. Mix your milk, sugar, eggs, oil, vanilla, sourdough discard and salt. You can add your brewed coffee now, but I like to wait and add it at the end.
Whisk it all together until fully combined. You can also use a stand mixer to mix this cake batter.
Now add your dry ingredients; flour, cocoa powder, baking soda, baking powder. Mix this into your wet ingredients and mix just until combined. Lastly fold in your chocolate chips using a rubber spatula.
Spray your mini bundt pans using a nonstick spray.
You can also add flour to the pans after greasing them to help release the cake from the pan. Pour the batter into the pans, fill them about 1/2 to 2/3 full.
Bake in the oven for 15 minutes.
Once the cakes are done, remove them from the pans. Let them cool on a cooling wire rack for at least 1 hour. You want the cake to be completely cooled before icing it.
I like to drizzle a chocolate ganache over the top of these mini bundts. You can get that recipe here!