Ohh dude.

First thing - don't use olive oil. Extra virgin olive oil mayonnaise tastes horrible & you can't trust light olive oil hasn't been blended with rapeseed.

Use liquid coconut oil (aka MCT oil). You can buy it in the supermarket these days.

My recipe (I usually 2x or 3x it) is:

1 egg

1 teaspoon of salt

1 teaspoon of Dijon mustard

1 tablespoon of lemon juice

Blend this with a stick blender & then while blending, pour in the oil until it gets to mayonnaise thickness. The more oil, the thicker it gets.

I've never had mine split.