I found this recipe for a 5-minute chocolate cake slice and I was pleasantly suprised with how good it turned out to be.
2T unsweetened cocoa
2T vegetable oil
2T chocolate chips
small splash of vanilla extract
Mix dry ingredients in a small bowl. Add egg and mix thoroughly. Mix in milk and oil. Add chocolate chips and vanilla and mix again. Pour into a coffee mug and microwave on high for 2 minutes. Allow to cool slightly and dump out onto a plate.