Prepare the vegetables by removing the hard stalk of the cauliflower and breaking it up into florets.
Discard any large cauliflower leaves but keep the little tender ones.
Place the cauliflower into a saucepan of salted boiling water and cook for 10 minutes.
While the cauliflower is cooking, remove the stalks from the kale and chop into rough strips.
Add the kale and cauliflower leaves to the pan for 2 minutes until just wilted.
Remove from the heat, drain and place leave to dry out - you don't want the extra moisture in your final dish.
To make the cheese sauce, melt the butter in a small saucepan then add the flour.
Beat until you have a thick paste, then slowly add the milk stirring regularly so that no lumps form.
Add the mustard and season well.
Next add the cheese and let it melt, again stirring regularly.
While the cheese sauce is cooking, heat the oven to 180 C / 350 F / gas mark 4.
Add the kale, cannellini beans and cauliflower to a roasting dish then pour over the cheese sauce and sprinkle with breadcrumbs.
Bake in the centre of the oven for 20 minutes.