I want chocolate

Well to know how to fix that you'd have to be more specific. How much of it are you having? Do you only eat junk food? Do you have chocolate more than once a day? Is it seriously effecting your health e.t.c.

I just had a chocolate cake 😋

They just make me feel happier.

Well if you're not overdoing it, I wouldn't call it an addiction. Coco in chocolate literally makes people happier because of chemicals in it that bring up you mood, it also does things like lower your blood pressure so it's literally a stress reliever. When it comes to things like junk food, yeah, it's gonna make you feel happier; the same would probably apply for any food you enjoy. Surprise surprise, when you like something, it makes you feel good when you indulge in it.

So it's not a problem that you enjoy them, that they make you happy; you shouldn't feel guilty about that, it's normal. What's important is making sure you moderate; don't become reliant on them, and if you have a lot of them, do things to make sure they don't affect your health; excercise more, make sure you don't spend too much of your day sitting around. (Side note, doing both of those things will also make you feel happier, so they can help break reliance on junk food)
TLDR: Being happy when you eat something you like is completely fine. Full on comfort eating however, isn't healthy. So if you moderate you're probably fine : )

I eat chocolate (Mars, Cadbury, Kinder and Twix) and chicken burger and chips from Mcdonald's or KFC every single day. I am addicted.

I am miserable without them. I can't function without chocolate and fast food.

Try to talk to people you trust irl about it; so that you can get help through breaking the habit. Try and find healthier alternatives that you still enjoy, try and wean yourself off of it by eating less of the stuff you do eat normally. If you really feel like you aren't making progress or that things are getting worse one way or another, then seak professional help with it.

Thank you for the advice

The only foods I crave is chocolate and chicken burger and chips. How to stop being addicted to junk food?