Why would this be a useful thing to know? Not all kitchens have large braising pans, electric skillets, or enough pots to cook it on the stove.
I use 4 inch chafing dishes/hotel pans and cook 10 to 15 pounds of meat in each one. Doesn't matter if its ground beef, ground chicken, ground pork, sausage...
Start with about half an inch of water in each pan...here I have 2x10# (2 packs of 10 pounds each) of Ground Beef (80/20 meat fat ratio). See my water pitcher in the background?
Take the meat and spread it out in pan. You can do this quickly it does not have to be "just so".
This is what it looks like in my oven. I do not cover the meat. The heated air works quicker and allows for some additional coloring and texture of finished meat(besides it looking a light gray from essentially oven steaming it). Yes! I keep a sheet pan in the bottom of my oven at all times for catching drips or mistakes...as you can see some on the pan, black spots.
And another "zoom out" view...
Let the meat cook undisturbed for thirty minutes, no matter what...you can adjust finishing time later. Depending on your oven, the temperature you use, kind of meat, et cetera...the time it takes to cook ground meat to proper internal temperature varies. I believe its 155 Fahrenheit for most ground meats except poultry, which I believe still has to reach 165. See how it looks kind of "meat loaf-ish"? Its time to pour as much juice/fat/water off as you can. Plus if you remove the liquid, its less dangerous using the masher to "ground" the meat! Ok, your thirty minutes has gone by...
Notice now we have most of the liquid and impurities drained off. Please don't feel like you have to drain the pan of liquid till every last drop of liquid is out, that defeats the purpose of this being easy and simple. See how the meat looks like a big loaf?
Time to turn that potato masher into a multi-tasker...Alton Brown would be so proud right now! I usually mash it down with the masher squiggles going one way, then mash the meat again with it going the other way...use the masher as a "rake" to move big chunks around for another mash if needed. This is when I would season the meat. After the first drain and mash. Back in the oven!
Its time to put the meat back in till its done all the way AKA (also known as) being at the proper internal temperature. This could be 15 minutes or more...depends on the meat and how many pounds you started with. But if your using a timer just set another 15 and check it again. NOW we are pretty sure the meat is done...drain it again if you think it has released more liquid than you want to keep in it.
Mash again. This is the second and last time. Once while cooking and again after the meat is done. Your now ready to use your meat, and/or let it cool, label & date, and put in freezer or fridge.
If your commercial kitchen is small like my current one, we do not use a fryer so we also do not have a grease pit that holds oils and fats until a big truck comes and services it(sucks it out). So, I let the fat separate naturally and then I ladle into a +Ziploc bag inside a +Cambro pitcher.
Then I throw it in a freezer till its solid, pull it out of the pitcher, and throw it away!