
When someone says that something was a piece of cake, they don't mean that someone gave them a brownie as a reward. If something was 'a piece of cake', it means it was very easy to do.

Paul: Congratulations on passing your driving test Maggie! And the first time, too. You must be over the moon.
Maggie: Thanks, Paul. Yes. I'm pretty pleased with myself. I don't know anyone else who's passed first time. My brother had three goes before he passed. He says he's happy I passed yesterday, but I think he's a bit jealous really.
Paul: You've done really well. I'm taking my test in about four weeks. I'm already getting workedup.
Maggie: There's no need. It was a piece of cake.
Paul: A piece of cake! You must be the first person ever to describe taking a driving test as 'a piece of cake'.
Maggie: No. It really wasn't difficult at all. I knew I would be okay as soon as I started. The examiner was very friendly. I did everything he told me to do and didn't make any mistakes. I was a bit worried about reversing round a corner, but that bit went fine. I know I'm a good driver and I'd have been surprised if I'd failed the test, too. Now I've got to save up to buy a car hopefully not a second-hand one, but we’ll see. That's the very difficult bit.
Jessica: Hi mum, it’s Jess. I’ve got some great news!
Mum: Hello, Darling. That’s lovely to hear – go on, what is it?
Jessica: It’s about that job interview yesterday. I thought I'd have to wait at least a few days before I heard anything either way. But the manager's PA herself called me half an hour ago and told me I'd got the job. I was speechless. It's a good job she likes talking because my brain froze when she told me and I couldn't even think, let alone speak. There were another four girls at the interview and a couple of them were very confident. And one of them had worked for the company before. Chatting before the interview, I knew I was up against some serious competition. But I felt very positive.
The manager who asked most of the questions was very pleasant and knew what he was talking about. The other three - two guys and a woman from the board of directors - didn't say much at all. They just sat there with fixed smiles on their faces and left the talking to Mr Chow. He asked me some searching questions, but I felt I answered all of them well. He kept nodding his head and smiling, so I thought I was doing well. But you can never tell in interviews.
I was in there longer than the three girls who'd been interviewed before me. It was a longish interview, but honestly it was a piece of cake because I was well-prepared and could answer all the questions I was asked.
Mum: Oh Jess, I’m so proud of you – though I told you you’d do well. So when’s your first day?