The proper way to get this involves using the patties that are bunched up on the ground in the walk in freezer. It's best to leave a bun set up already on the sandwich prep station as well.
- Fail 3 orders, easy way is to do this is to just pack up 3 drinks or shakes and send those out.
- That will trigger the appearance of Happy.
- Immediately run to the walk in freezer and aim at the pile on the ground on the ground and pick up at least 2 or more to be safe.
- From there you need to run back to front asap and goad/bait Happy into following you be keeping a direct view on her, do so to a position where you can keep direct view on her and the grill, and toss the patties on the grill.
- Toss at least 2 on the grill to give yourself a good chance as it make take a few tries. Space each placement a few seconds apart to allow good targeting.
- You'll know you're doing it right if the patties catch on fire, now you wait until the fire turns green then pick em up and hold them or backpack them.
- Keep your eye on happy and place ALL the fixings on the bun in any order including the meat, finish it and toss it at her.
You only need 1 Burger, enjoy your achievement.