You screw up your courage and eat the black pudding. It turns out to be the blood sausage sort of pudding. You're not positive that that's a good thing. Bleah.
Consuming this from your inventory spawns the black pudding monster approximately 35% of the time. However, consuming from Chez Snootée in Little Canadia does not seem to spawn the monster.
Eating a black pudding requires one adventure, but the adventure is only used if you enter into combat with your meal.
If you have no adventures, you will be told "You don't have time to properly enjoy a black pudding right now."
If you are beaten up, you will be told, "You're way too beaten up to enjoy a black pudding right now. Because they're tough to chew. Yeah."
Combat can still be initiated when eating this food while falling-down drunk.
References
The "acidic underground-dwelling scavenging ooze" refers to the Dungeons & Dragons black pudding monster, an amorphous blob which roams caves and sewers and absorbs and digests whatever (or whomever) it finds.
It also refers to a strategy within Nethack of Pudding farming by repeatedly dividing and killing black puddings for stats.