2) In a large bowl, combine all of the ingredients. Beat at medium speed with an electric mixer until smooth. Fill cupcake cases about two-thirds full. Bake for 16-18 minutes, or until a wooden pick inserted in centre comes out clean. Let cool in pans for 10 minutes. Remove from pans and let cool completely on wire racks.
3) For the icing, in a medium saucepan, combine sugar and cream. Bring to a boil over medium-high heat; reduce heat and simmer for 6 minutes, stirring frequently. Remove from heat; add chocolate and butter, stirring until melted and smooth. Let cool for 10 minutes. Whisk in icing sugar. Let mixture cool until it reaches a spreadable consistency, then top cooled cupcakes with icing.
4) For the topping, place biscuits into a resealable plastic bag. Crush with hands to make a 'dirt' consistency. Sprinkle icing with biscuit crumbs, top each cupcake with a gummy worm and enjoy.