Preheat your oven to 350°F (175°C). Line a standard 12-cup muffin tin with black or festive Halloween cupcake liners to keep the theme consistent and prevent sticking.
In a medium mixing bowl, sift together the flour, sugar, dark cocoa powder, baking soda, and salt. Sifting the cocoa powder is important as it tends to clump, and you want a perfectly smooth batter for the best color distribution.
In a separate large bowl, whisk together the vegetable oil, buttermilk, eggs, vanilla extract, and white vinegar until well combined. Gradually add the black gel food coloring to the wet mixture until you achieve a very deep, dark hue.
Slowly add the dry ingredients into the wet ingredients. Use a whisk or an electric mixer on low speed to combine them until the batter is smooth. Be careful not to overmix, as this can make the cupcakes tough.
Divide the batter evenly among the cupcake liners, filling each about 2/3 of the way full. Place the tin in the center of the oven and bake for 18 to 22 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cupcakes from the oven and let them cool in the tin for 5 minutes. Then, transfer them to a wire rack to cool completely. They must be entirely cold before you attempt to frost them.
In a large bowl, beat the softened cream cheese and butter together until smooth and creamy. Gradually add the powdered sugar one cup at a time, followed by the vanilla. Add black gel food coloring and mix until the frosting is a deep, midnight black.
Fit a piping bag with your favorite tip and frost the cooled cupcakes. You can add spooky sprinkles, edible silver glitter, or small plastic spiders to enhance the Halloween vibe.