The act of pooping in a dixie cup (and or any other paper/plastic cup, because you don't want use a glass for sanitary reasons *poop is hard to wash off of dishes*) and have your partner finger the poop cup, licking his/her's finger's in-between each stroke. Meanwhile you urinate/ejaculate (whichever your preference is) onto their head.
"hey sally you want to go bake in a cup?"
sally:"sure... like what? cookies? muffins?"
sally:"yeah... I'm not gonna do that"
baking in a cup