Preheat oven to 180⁰C. Line a 18cm round baking tin with grease proof paper.
In a large bowl melt the margarine in a microwave. Then stir in sugar, eggs, and mix together. Then add sift cocoa, sift flour, salt, and baking powder to mixture. Mix together well. Spread batter into prepared pan.
Bake in preheated oven for 50 to 55 minutes until cooked.
To Make Frosting:
Beat the butter in a large bowl until soft. Add half of the sift icing sugar and beat until smooth. Add the remaining icing sugar and beat the mixture until creamy and smooth. Stir in the food colouring and orange extract until well combined. If needed you can add a little more colouring to make a stronger colour.
When the chocolate cake has cooled, cover in orange frosting. Add a line of Smarties around the base of the cake. To make the scary pumpkin, cut small holes in the satsuma and insert mini smarties to make a face. Use writing icing to draw a triangle for the nose. Place a large and two mini smarties on the top of each other to make the stalk. Draw a spider web with the melted chocolate or writing icing over half the cake and add mini smarties to the web. Make the spiders and creepy crawlies using smarties and writing icing.
To make a spider place a smarties on the cake, draw two eyes on the smarties and then draw four legs each side of the smarties. Do the same process to make creepy crawlies, draw the eyes on the smarties and add legs. You can use mini smarties for the head and larger ones for the bodies and a row of mini smarties for the caterpillar. You can create you own design of insects.