Grease your bundt pan thoroughly with butter or non-stick spray, then dust with cocoa powder to prevent sticking. Preheat your oven to 350°F (175°C). Ensure butter, eggs, and buttermilk are at room temperature.
In a large bowl, sift together cake flour, cocoa powder, baking powder, baking soda, and salt. Whisk to evenly distribute.
Cream softened butter with granulated sugar and brown sugar on medium speed until fluffy and pale, about 3-4 minutes.
Beat in eggs one at a time, mixing well after each addition. Add espresso powder and vanilla extract, blending until combined.
In a separate bowl, whisk together buttermilk, vegetable oil, and Greek yogurt until smooth.
With mixer on low, add dry ingredients in three additions alternating with wet ingredients in two additions, beginning and ending with dry. Mix just until combined.
Gently fold in mini chocolate chips with a spatula.
Pour batter into prepared bundt pan and smooth top. Bake 50-60 minutes or until a toothpick inserted comes out clean or with a few moist crumbs. Cool in pan 15 minutes, then invert onto cooling rack to cool completely.
Heat heavy whipping cream in a small saucepan over medium heat until just simmering. Remove from heat and pour over semi-sweet chocolate chips in a heatproof bowl. Let sit 2 minutes, then stir until smooth and glossy. Stir in vanilla extract.
Once cake is completely cooled, drizzle ganache evenly over top, allowing it to cascade down the sides. Garnish with extra mini chocolate chips or sprinkles.