Depends on who I use. If I use a "helper" sim, I usually just let the drained moodlet fall off by itself in 2 days - but remember DO NOT let that helper with the drained moodlet eat cake again, he/she will die. If I don't have helper or I need another essence fast, I will drink moodlet solver to clear the drained moodlet and can eat cake again to get a different essence.
If you are doing dynasty, it is worth the time to get a cloning machine. With one cowplant essence, you can clone the essence as much as you want -- let the drained moodlet fall off by itself and save your moodlet solver for other emergency situation.
The important thing about the essence is it gives a 12 hours moodlet. Most of the other moodlets are 4 hours (some 6), they don't last the whole workday. I need something that last very long and cowplant is the only one I found that gives the "target" moodlet and last that long. The other long ones (like have baby, newlywed, etc.) are just +happy moodlets.