This sounds exactly like what happens in our house on a regular basis, be it over banana not presented in the skin like a monkey, toast cut into sqaures rather than triangles, milk put on the rice bubbles when she doesn't want milk .... the list goes on!

My response is fairly similar to yours. I calmly talk to her and ask if that's how she asks for something which generally calms her down enough to say "I don't want milk please mummy" so if she does that then I will generally change it (unless of course the request it totally unreasonable). If she continues with the screaming and tantrum then I will tell her she's in the corner if she doesn't stop it. If she doesn't stop it then she goes in the corner until she has calmed down and is ready to say sorry.

I try to remain calm and reasonable but I do sometimes end up yelling at her which isn't ideal - they really know how to push your buttons don't they?