To start, go to Lumbridge Castle (the starting place) and talk to the cook.
Cook: What am I to do?
Player: What's wrong?
Cook: Ooh dear I'm in a terrible mess
Cook: It's the duke's birthday today
Cook: I'm meant to be making him a big cake for this evening
Cook: Unfortunately I've forgotten to get some of the ingredients
Cook: I'll never get them in time now
Cook: I don't suppose you could help me?
Player: Yes, i'll help you
Cook: Oh thank you, thank you
Cook: I need milk, eggs and flour
Cook: I'd be very grateful if you could get them to me
Take the pot which is in the room and go to the General Store with 2gp. Buy a bucket and go east where there should be a cow field. Go in it. Use the bucket with a cow and you should get milk in a bucket. Opposite the cow field is a chicken farm. Go in there. There should be an egg. Take it. You now have the milk and the egg. To get the flour, go south from the chicken farm, then go west, then north and then west again at the cabbage field. There should be a wheat field, pick 1 wheat, and go in the circular building east of the wheat farm. Go in there and go up 2 ladders to get to the top. Use the grain with the hopper, then operate the hopper by right clicking and pressing operate hopper. Now go down 2 ladders to the bottom and use pot with the flour. Now go back to the cook and talk to him.
Cook: How are you getting on finding the ingredients?
Player: I now have everything you need for your cake
Player: Milk, flour, and an egg!
Cook: I am saved, thank you!
You gain 3 cooking levels and 1 quest point.