Cress, sorry its a stupid question.

When we buy a little carton of cress it has flat not curly leaves but no mustard flavour

I am growing cress which has flat leaves but a mustard tang. 

I wanted the flat variety without the taste but all i can find is curly leaf variety with no mustard taste

I know this is daft but can we eat the mustard type and what is the type shops have

I know its daft but i need to know. 

Most of the shop "cress" is actually oil seed rape.

Oh  The kids want shop type cress, can i buy seeds and grow that the same