1. Preheat oven to 350°F (175°C); line a 12-cup muffin tin with cupcake liners.

2. Whisk flour, cocoa, baking soda, and salt in a bowl.

3. In another bowl, whisk sugar and oil; beat in eggs, buttermilk, red coloring, vanilla, and vinegar until smooth.

4. Fold dry ingredients into wet just until combined; divide batter among liners (about 2/3 full).

5. Bake 18–20 minutes, until a toothpick comes out clean; cool completely on a rack.

6. For frosting, beat cream cheese and butter until fluffy; mix in vanilla and salt, then gradually add powdered sugar to a smooth, pipeable consistency.

7. Core each cupcake center with an apple corer or small spoon; fill each with jam and replace a bit of cake as a plug.

8. Frost cupcakes smoothly or pipe swirls; create two small “fang” punctures on top.

9. Add red gel or thinned jam to the punctures to drip like blood; finish with fangs or sprinkles.

10. Serve at cool room temperature; refrigerate leftovers in an airtight container for up to 3–4 days.