Mrs.Cake's got the bowl of batter right under her big, beautiful, blue butt. You watch in awestruck arousal as she squats lower, spreading those luscious orbs of pudge and revealing her tight little stink star. She starts to clench, biting her lower lip as she attempts to force something nice and big from her bowels. A nice, deep fart sputters out against the batter, sending ripples through it, but nothing seems to come out. A few more brassy toots that stink of something ripe, but not the payload you were expecting. She grunts once more, but still nothing.
Mrs.Cake looks to you, "I did say you'd be putting that tongue of yours to good use, now come here and help me coax our special ingredient out."
"Happily!" You reply. You dive down underneath her and spread her cheeks a little further so you can really get in up against her balloon knot. Her butt still smells like her previous bowel movements, but it's surprisingly clean. You can hear gurgling in there, she's holding on to something delightfully large and you just can't wait to get it out in the open.
Your tongue flicks out against Mrs.Cake's sphincter and she coos, blowing a nice little fart against your nose. It burns, but in a very nice way. Like spicy, rotten milk. She giggles and gives you another puff of rancid flatulence as incentive to keep slurping away at that pucker.
"Mmn," Mrs.Cake pats her swollen belly, "I think I feel it. Oh Celestia, this is going to be like giving birth!"
Her anus unclenches and gives you a real nostrilfull of her distinct, scatty scent. You can see the enormous turd start to poke out of her butthole. You lick around her anal ring as it starts sliding out, relaxing it a little more. She's pushing out a really enormous log, it's got to be at least the size of your cannon, thick and dark brown. She must have been preparing this little "secret ingredient" for some time.
"How does it look, sweetie?" She says, between her moans. "Big enough for the shortbread?"
"Plenty!" You say, still licking at her anus(and sneaking a few nibbles of her bitter chocolate log). She pushes one last time and the remainder of the delicious load slides out. It drops into the bowl,(along with a bit of liquid feces and a couple of especially wet farts) and then Mrs.Cake can finally stand up. Wow, you actually think she shed a good two pounds with that titanic load.
"Ah, now we can get this ready..." She starts to sing a little while she fetches her mixer and whips the chunky scat into her shortbread batter, thickening it and darkening it considerably. Then she places little dollops of it onto the cookie tray and slips it into her oven. You get to lick the bowl of course, and lick it clean.
"You know," Mrs.Cake says, "if you'd like you could make some treats of your own. That is, if you've got any special ingredient in you."
You look up from your bowl of chocolate batter and respond,