In a bowl beat the butter. Add caster sugar then cream the butter and sugar together. Add the eggs and mix well. Add vanilla, flour, and milk. Beat until smooth.
Place individual paper baking cups in a muffin tray and pour in the mixture until they are about 2/3 full. Bake in the oven at 190°C for 20 minutes or until golden.
While the cupcakes are cooling on a wire rack, prepare the frosting.
Microwave the chocolate on high for 1 min. Cream the butter and sugar together, then beat in the melted chocolate. Pipe a circle of frosting on to the tops of the cooled cupcakes. Place one chocolate Easter egg in the center.