Preheat and prepare pans: Heat your oven to 350°F (175°C). Line a 12‑cup muffin pan with cupcake liners and lightly spray around the liners with non‑stick cooking spray.

Mix dry ingredients: In a large bowl, whisk flour, sugar, cocoa powder, baking soda, and salt until everything is well blended.

Add wet ingredients: Pour in the buttermilk, vegetable oil, egg, and vanilla. Use a whisk to break the egg yolk, then whisk until the mixture is smooth and no large lumps remain.

Fill cupcakes: Divide the batter among the muffin cups, filling each about ⅔ full.

Bake: Place in the preheated oven and bake until done, about 19‑23 minutes. A toothpick inserted into the center should come out with a few moist crumbs clinging to it, but no visible wet batter.

Cool: Let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack and cool completely. Decorate only when fully cooled.

Make decorations:

• For cat ears: Split Oreos in half, remove filling, cut into large triangles for ears.

• For bat wings: Cut Oreo halves (without filling) into half‑moon shapes.

• For jack‑o’‑lantern faces: Use Oreo triangles for eyes and nose; cut curved scraps for mouths; pretzel stick as stem; green M&M’s for leaves; edible marker to draw eye details.

Make frosting: In a large bowl, beat together powdered sugar and butter. Add 2 Tbsp heavy cream, salt, and vanilla (or orange zest + extract). Mix until smooth. Add gel food coloring to achieve bright orange. Add extra 1 Tbsp heavy cream near the end if needed for consistency.

Pipe or spread frosting: Fit a piping bag with a star tip (e.g. Ateco 846) and pipe a single star‑layer swirl on each cupcake, or simply spread with an offset spatula. Reserve about 2 Tbsp frosting for “glue” to attach decorations.

Decorate:

• For cat cupcakes: Place a whole Oreo on the cupcake, tuck two Oreo‑triangle ears, use a dab of frosting to attach green M&M eyes and sprinkle for nose or pipe a small nose.

• For bats: Place Oreo body, tuck wing shapes underneath; add eyes and sprinkle or pipe mouth.

• For jack‑o’‑lanterns: Add triangle eyes and nose, curved mouth scraps, stick pretzel “stem,” position green M&M “leaves.”