The contemplations on foulness aren't really relevant to your cookie example.
With respect to the frames of reference, mindfulness could include.....
Mindfulness of body - the physical movements and posture involved with eating the cookie, biting it, swallowing it etc.
Mindfulness of feeling - the taste of the cookie, the texture of the cookie, the feeling in your mouth, throat or stomach
Mindfulness of mindstates - is the mind dull, craving, depressed etc? whilst eating the cookie
Mindfulness of mind object - observation of each thought as it arises and it's qualitative nature
Consciously choosing to put down the cookie will probably happen if you do the latter of the 4, and you observe, with wisdom, that eating the cookie is not the most wholesome action to perform (because it is rooted in craving and will lead to suffering)