Step 1

Preheat oven to 160C (140C fan-forced). Grease and line a deep 22 cm x 28 cm slab pan.

Step 2

Melt butter and chocolate together in large bowl in microwave on 70% for 3-4 minutes, stirring with a metal spoon every minute until almost smooth.

Step 3

Add cocoa and whisk until smooth, add sugar and mix well.

Step 4

Add half of egg mixture, stir to combine, repeat.

Step 5

Sift flour over mixture, stir gently until just combined.

Step 6

Pour into prepared pan.

Step 7

Arrange chopped Mars Bars over cake batter and press in slightly.

Step 8

Bake for 60-65 minutes or until a skewer inserted off centre has moist crumbs clinging to it. Cool completely in pan, then cut into squares.

Step 9

To make cupcakes use muffin pans lined with papers, baking for 25 minutes.