whichever? whatever?

I think a relative pronoun 'which' is different from 'what'. Since 'what' includes the antecedent but 'which' does not. Therefore, in an example;

EX: 'Add garlic to what you're making.' is OK, but,

'Add garlic to which you're making.' is not good.

Then, my question is, what about 'whichever' and 'whatever'?

For the above example, both look OK. That is,

EX: 'Add garlic to whatever you're making.' --(A) looks good

and 'Add garlic to whichever you're making.' ---(B) also looks good.

What is grammar? Both (A) and (B) are OK. Or just (A) is correct. If (A) only is correct, why is that?

Help me please, and thank you!