Add the onion and leave it there until translucent, add the pepper and the beans.
Leave in the pan for two or three minutes and add the salt.
Start putting the kale leaves and let them wilt. If they do not fit all at once, add them little by little. First one handful, then the other and so on.
Before making the sandwich, make sure there is no liquid in the pan.
To make the sandwich, toast two slices of bread. When they are ready, spread dijon on each side and top it with one or two tablespoons of the sauteed kale mixture.