Break cauliflower into small pieces, about ½" - ¾" thick. Don't use the thick inner stem, just add it to your compost pile.
Salt a pot of water and bring it to a boil, then add the cauliflower pieces to the boiling water and cook for about 10-15 minutes, until just fork tender. Drain and reserve.
In a large mixing bowl, whisk together the eggs, flour, half and half, cheese, ham a pinch of salt (don't add too much since the cheese is salty), and a few turns of freshly ground black pepper.
Add the drained cauliflower to the bowl and toss to combine, then pour the entire mixture into a buttered gratin dish.
Bake 25-30 minutes at 400°F until the egg mixture sets. When it is done it won't jiggle if you shake the pan, and a toothpick or cake tester should come out clean.