Preheat your oven to 350°F. Line a 9x13-inch metal baking pan with parchment paper, and then give it a light greasing or a good spray with nonstick baking spray.

To make the cake batter, grab a large bowl and whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.

In a separate smaller bowl, whisk the eggs, buttermilk, coffee, oil, vanilla extract, and mint extract until nicely combined.

Now, pour the wet ingredients into the dry ingredients and whisk everything together by hand or on low speed with an electric mixer.

Keep going until the batter is smooth and no dry streaks of flour or cocoa powder are left. Don’t worry if the batter seems thin — that's exactly how it should be!

Pour the batter into your prepared pan and pop it in the oven. Bake for 33 to 36 minutes, or until a tester inserted into the center comes out with just a moist crumb or two.

Once baked, place the cake (still in the pan) on a wire rack and let it cool completely before frosting.

While the cake cools, let's whip up the mint buttercream frosting! Using an electric mixer on medium-high speed, beat the butter until it’s pale yellow and fluffy — this should take about 2 to 3 minutes.

Add 1 cup of confectioners' sugar and 1 tablespoon of heavy cream, then crank up the mixer to high and beat for one minute.

Add another cup of sugar and another tablespoon of cream, beat again, and keep repeating until you've added all the sugar and cream. Now, toss in the salt, mint extract, and green food coloring, and mix on high for another minute.

Add a bit more food coloring if you want a deeper minty green shade. If your frosting feels too thick, mix in another tablespoon or two of cream.

If it feels a little too soft, just add an extra tablespoon or two of confectioners' sugar until it's just right.

Finally, with the mixer on low speed, gently mix in the chopped Andes mints or dark chocolate until evenly distributed.

Once the cake is completely cool, spread the mint frosting generously over the top using an offset spatula.

For a fun finishing touch, swirl the frosting with the back of a spoon and sprinkle over more chopped Andes mints or a handful of shaved chocolate. Enjoy!