Onion does not make them fall apart.
I use good quality mince . If it comes from asda or tesco yer **** already as I’ve never had good mince from there. Always dry grey tasteless crap.
If you use low fat lean meat your burgers will be dry and crumbly.
I make 30 odd burgers every couple of weeks for the burger night at work. What I’ve settled on for a recipe is 3kg good mince ,2 beaten eggs for binding also 5 oatcakes crunched up one small onion , 2 cloves garlic a small green chilli and a chipotle chilli all blitzed in the blender and added in then I mix them up by hand and lay them into tin foil shaped by hand and sprinkle lightly with salt
I cook them for about 10 min in tin foil on the braai then move the grill down close to flame and lay them direct on the grill. Give them a squash with the spatula and the fat runs into the coals it flames up and chars them .
Before lifting off be sure to put your cheese on while on the heat let it melt into the top of burger
Cut your bun in half and stick it on the grill for a few minutes to toast it – stops that falling apart
Eat 🙂
The other thing – if you use good meat your burgers are unlikely I shrink like shop bought ones which are full of water to plump them up. So shape them the size of your roll rather than over size and get them nice and thin as I also find they tend to swell