The seminal fluid that is ejaculated deep into ones throat after giving successful oral stimulation.
"Hey bitch! you know that the best remedy for your dry throat is coating it with some of my sweet throat Butter. Now, slob on my knob!"
Flem coughed up and spit into hot tea. The hot tea is then considered to be flavored with throat butter.
I ran out of milk today, so instead i coughed up some throat butter for my morning tea.