Cauliflower florets
With care — Allowed by some hospitals and not others, or allowed only prepared a particular way.
In one line: Use florets only, with no stalk. Cook until soft.
Stoma note: Can increase wind.
The head and the stalk of a cauliflower behave completely differently. The floret is a mass of undeveloped flower buds with short fine fibres that soften readily. The stalk and the core are structural, built to hold the head up, and stay tough however long you cook them.
The preparation
Florets only, no stalk. Cut the head into quarters, cut the core away and throw it out along with the thick stems and the leaves. What you keep is the button of curd with no more than a centimetre of stem. Cut them to an even size and boil or steam for eight to ten minutes, until a knife slides into the thickest floret and meets no resistance at all. Past the point most cooks would stop. See florets only, no stalk.
Where hospitals differ
This is one of the sharpest splits in the whole diet. The leaflet this book follows allows florets cooked soft, as does St George's, which classes them as medium. Leeds lists cauliflower on its avoid list even at the least restrictive stage of its obstruction diet.
There is a second question underneath. Cauliflower is a brassica and brassicas are flagged for wind in stoma advice regardless of how well they are cooked. Passing the texture test does not settle the wind one.
If you have been told to leave it out
Potato does a similar job in a soup, and the cheese sauce, which is the part most people are actually after, works over anything. See brassicas.