There are 4 million hits for the precise phrase "cook up your own": http://tinyurl.com/33pwx3r
most of these used figuratively as in your own example.

--------------------------------------------------
Note added at 2 hrs (2010-11-18 17:23:25 GMT)
--------------------------------------------------

The culinary image of ‘cooking something up’ is no more and no less bizarre than the German ‘backen’. Regarding Mr Toogood’s offering, I am not sure that it is legitimate to switch the ‘dream’ element from the noun to the verb. In any case, ‘Traum-’ is an overused prefix in German that normally requires a different treatment in English (perfect, ideal, fabulous etc).

If I understand the idea behind ‘backen’ correctly, it is to mix together the right ingredients in a recipe or even a (magic) formula. This is not the same as performing a conjuring trick, let alone sinking into reverie.

And if you are keen to retain the 'salopp' register, I commend Nicole Schnell's suggestion for Traumpartner: Mr Right.

--------------------------------------------------
Note added at 4 hrs (2010-11-18 20:05:10 GMT)
--------------------------------------------------

One more to throw into the mix before someone else does

to concoct: cook up (prepare or cook by mixing ingredients)
http://wordnetweb.princeton.edu/perl/webwn?s=concoct

More gehoben than salopp