Cauliflower Gratin with Garlic and Feta

We are addicted to this comforting winter dish that uses all parts of the cauliflower, not just the florets. The first time I made it with anchovies to spice up the cauliflower’s sweetness. I liked it a lot, but Costas definitely prefers the feta version, so I begin there. It is inspired by a broccoli-and-potato gratin from Provence described by Guy Gedda in La Table d’un Provençal.