Peel the aubergines in alternating stripes, then cut them into 2cm-cubes and transfer to a large bowl.
Sprinkle with 1 tablespoon (14g) of the salt and toss well with your hands to distribute the salt evenly.
Tip them into a colander and place it on top of the used bowl to catch any juices. Set aside.
Heat 2 tablespoons of the olive oil in a large casserole over medium-low heat.
Peel and finely chop the onion and sauté it in the oil until it turns translucent (8-10 minutes).
Add the walnuts to a food processor and blend until they turn into a coarse paste, grinding until some start breaking down into walnut butter.
