Follow instructions in linked recipe to make the chocolate cake. Place cooled baked cake onto a serving platter and set aside.
To make the chocolate sour cream frosting, mix butter, cocoa powder, and powdered sugar together 1-2 minutes to incorporate butter throughout the sugar. The mixture will be dry. Stir in vanilla and sour cream. Scrape sides and whip 2 minutes or until completely smooth. Spread frosting over the entire cake.
In a small bowl, whip all ingredients for the orange frosting {carrots} until smooth. Spoon into a piping bag fitted with the Wilton 1A tip {wide round tip}. Pipe 3 to 4 rows of 3 even rounds or dollops onto the chocolate frosting creating the tops of the carrots. Top each carrot with a sprig of mint. Spread crushed oreo cookies around each frosting carrot to create the dirt.
Finally, line the edges of the entire cake with mini Cadbury eggs. Cut into pieces and serve.