Vampire fudge cake
Wait 'til your girlfriend is on her period, and feed her nothing but fudge for three days, forcing her to hold any shits in. When the three days are up, make her squat above your open mouth, then have her release a mixture of period-blood and the fudgey goodness that is now her shit into your mouth.
Reece: Have you started your period yet?
Abi: Yes. Why?
Reece: Because I want a vampire fudge cake, you fucking whore.
Abi: Yes. Why?
Reece: Because I want a vampire fudge cake, you fucking whore.