Position a rack in the center of the oven and preheat to 350°F. Line a 12-cup muffin tin with paper liners.

In a medium mixing bowl, sift or whisk together the cake flour, black cocoa powder, baking powder, baking soda, and kosher salt. Set aside.

In a large bowl, whisk the vegetable oil, room-temperature eggs, and vanilla extract until fully combined and glossy.

Add the granulated sugar, buttermilk, and white vinegar, and whisk until the sugar has dissolved and the mixture is smooth.

Fold in the dry ingredients with a spatula or whisk until just combined, taking care not to overmix. The resulting batter will be thin and loose.

Divide the batter evenly among the prepared liner cups, adding about 1/4 cup (60 ml) of batter to each so they are roughly half full.

Bake in the preheated oven for 18 to 22 minutes, until a toothpick inserted into the center of a cupcake comes out clean.

Let the cupcakes cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.

Ensure the cupcakes are completely cool before applying the cream cheese frosting.

Pull the butter and cream cheese out well ahead of time so they are both at room temperature; this prevents lumps in the frosting.

In a large mixing bowl, beat the softened butter and cream cheese together with a hand mixer or a stand mixer using the paddle attachment until the mixture is completely smooth and creamy.

Add the sifted powdered sugar, vanilla extract, and salt, and mix on low speed until everything is incorporated and no dry sugar remains.

Turn the mixer to high speed and whip for 4 to 5 minutes, until the frosting becomes pale, light, and fluffy.

If needed, beat in 1 to 2 tablespoons of heavy cream, a little at a time, until the frosting reaches a smooth, spreadable consistency.

Frost the cooled cupcakes with the prepared cream cheese frosting and decorate with candy eyes to create ghost faces.