Leether Cream

This doesn't exist in Minecraft; it's just fiction.

'Leether Cream or Yellow Slimeball '''is a Ball of Slime obtained by killing a Leether Slime. 0-2 slimeballs drop when a small Leether Slime is killed. The slimeball cannot be thrown. As slimeballs come from a mob, they are a renewable resourse .

Brewing
They are used for brewing the Potion of Thickness which is very stronge.