This is the mud cake recipe I used (I don't think I've made this one before Bel, so I'm claiming this one in the challenge..) . It's from an old book called Eat GST-free by Sophie Ruggles.
250g unsalted butter
2 cups white sugar
1 tsp vanilla essence
1 1/2 cups plain flour
1/2 cup cocoa
pinch of salt
1. Preheat oven to 190 deg C. Grease a large round cake tin well and fully line with greaseproof paper.
2. Combine butter and sugar in a large bowl and beat together well until creamy.
3. Add eggs and vanilla essence to butter mixture and mix together.
4. Sift flour, cocoa and salt into separate bowl, make a well in the middle, pour in butter mixture and beat together until smooth.
5. Bake in oven for 30-40 minutes.
Unfortunately I didn't get a photo, but it's a fudgey type chocolate cake - mmmm!