01 - Preheat the oven to 350°F. Grease a mini bundt pan thoroughly with butter or nonstick spray.
02 - In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.
03 - In a large bowl, beat the softened butter and sugar together until light and fluffy, about 3 minutes.
04 - Add eggs one at a time, mixing well after each addition.
05 - In a separate small bowl, combine buttermilk, vanilla extract, vinegar, and green food coloring.
06 - Add half of the dry ingredients to the butter mixture, mixing just until combined. Pour in the buttermilk mixture and mix briefly. Add the remaining dry ingredients and mix until smooth.
07 - Spoon the batter evenly into the prepared mini bundt pans, filling each about two-thirds full. Bake for 18–22 minutes, or until a toothpick inserted into the center comes out clean.
08 - Cool cakes in the pan for 10 minutes, then carefully invert onto a wire rack to cool completely.
09 - Whisk powdered sugar, milk, and vanilla extract until smooth and pourable. Drizzle over cooled cakes.
10 - Decorate with green and gold sprinkles as desired.