Preheat your oven to 140C Fan/325F/Gas Mark 3, and line a cupcake tin with cupcake cases, ideally black ones for that perfect spooky touch.
In a mixing bowl, combine the baking spread and caster sugar using an electric mixer until the mixture is smooth and fluffy, which should take about five minutes.
Add the eggs one at a time along with the vanilla extract, whisking thoroughly after each addition to ensure everything is well incorporated.
Gently fold in the self-raising flour using a spatula or wooden spoon until just combined before adding black food coloring; mix until you have an even color throughout.
Spoon equal amounts of batter into each cupcake case and bake them in your preheated oven for 25-30 minutes or until a skewer inserted in the center comes out clean; let them cool completely on a rack afterward.
Once cooled, use a cupcake corer or knife to create holes in each cake before filling them with lime-colored custard mixed with green food coloring; finish by piping bright green buttercream on top decorated with candy eyes and sprinkles for an eye-catching finish!