Translation:Follow the recipe.
Reminds me of 사잇소리 (the insertion of ㅅ inside compound words, which 사이ㅅ소리 itself is an example of) though I’m only aware of this happening to compounds containing at least one native Korean morpheme and some exceptional cases of pure Chinese-derived compounds (e.g.: 숫자). That the dictionaries acknowledge the [뻡] pronunciation is interesting considering the lack of any clues in the spelling; the following initial consonant should only be tensified if it is preceded by another consonant. Compounding the problem is that (as you said) “법 is usually pronunced as [뻡],” but not always:
- 가법 (加法) is [가뻡]
- 가법 (苛法/假法) is [가ː법]
- 가법 (家法) is [가법]
For consistency, 요리법 should be 요릿법 if spelled out to be consistent with pronunciation, or 료리'법 in the north’s orthography proposal (조선어신철자법). But orthographic reform has been on the back burner for a while.
EDIT: Readers of this post, please do not take this as advice to mispell words.
조선어신철지법 (North Korea's New Orthography) was abandoned almost 70 years ago and even before that it saw little use, and we rather won't see it returning. Though the idea of using ' (apostrophe) as an indicator of stressed sound was apparently considered in the 1960's, right after North Korea scrapped the "middle-ㅅ" whatsoever. Again, it was abandoned very quickly. Therefore current spelling is 료리법.
On a side note, no matter of underlying 한자, 가법 is always pronunced as [가뻡] in North Korea (according to 조선말대사전).