Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners.

Cream together the softened butter and sugar until light and fluffy, about 2-3 minutes. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract and red food coloring.

Whisk together the flour, cocoa powder, and salt in a separate bowl. Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk, until just combined.

Stir in the baking soda and vinegar mixture. Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.

Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool in the pan for 5 minutes before transferring to a wire rack.

In a small bowl, combine the red velvet cake crumbs with sweetened condensed milk and melted butter. Stir until smooth and glossy. Add red food coloring for intensity.

Use a small knife or cupcake corer to remove a small section from the center of each cupcake and fill it with the creamy filling.

Beat the softened butter until creamy. Gradually add the powdered sugar, mixing well. Add vanilla extract and milk or cream, then beat until smooth.

Add a few drops of ivory or peach food coloring for a pale color.

Frost each cupcake with the pale buttercream until smooth.

Use candy fangs or drops of red gelatin to create puncture marks, drizzle red syrup or gel from the marks.

Arrange the cupcakes on a dark serving platter and surround with additional red drips for a spooky effect.