[a confused chiral girl]

Hi there~

I did this question reacting with KOEt, and that's the product I got below in the diagram. However, I checked the books and it says that there is that side product formed. I don't understand how that side product is formed, can anyone please explain it to me?

So does this mean that...KOEt shouldnt be used in this reaction, and we should use another base in this Claisen reaction to get the product that I first predicted will form? 

[Yggdrasil]

Look up transesterification.

[kremar]

specificaly, base-catalyzed transesterification.

[burnt]

Use MeOK(Na) instead.