Make the Chocolate Cake Batter:

1. Preheat oven to 350°F (175°C). Grease and flour a 6-cup mini bundt pan.
2. In a bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
3. In another bowl, whisk together granulated sugar, brown sugar, buttermilk, coffee, oil, eggs, and vanilla extract until smooth.
4. Gradually add the wet ingredients to the dry ingredients, stirring until fully combined.
5. Fold in the mini chocolate chips.
6. Spoon batter into the mini bundt cake molds, filling each about ¾ full.

Bake the Cakes:

7. Bake for 18-22 minutes, or until a toothpick inserted comes out clean.
8. Let the cakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.

Make the Chocolate Ganache Filling:

9. In a saucepan, heat heavy cream until it just starts to simmer.
10. Remove from heat and pour over the chopped chocolate in a bowl. Let sit for 2 minutes, then stir until smooth.
11. Stir in vanilla extract and let cool slightly.

Fill the Cakes:

12. Once the cakes are completely cool, use a piping bag or spoon to fill the center of each mini bundt cake with chocolate ganache.

Make the Chocolate Glaze:

13. Heat heavy cream in a saucepan until warm but not boiling.
14. Pour over the chocolate chips, let sit for 1 minute, then stir until smooth. Add corn syrup for extra shine if desired.

Glaze and Decorate:

15. Drizzle the chocolate glaze over each mini bundt cake.
16. Garnish with chocolate shavings, mini chocolate chips, or whipped cream.