Preheat the oven to 350F and lightly grease a 9x13 pan or other large casserole dish.
Place half of the cauliflower florets in a food processor and pulse a few times on high until coarsely chopped. Transfer to a large bowl and repeat with the remaining cauliflower. (It's okay to have some bigger pieces in there...)
Add the ham, half of the cheese, and the garlic. Sprinkle with the salt, pepper, and glucomannan and toss to combine. Fold in the sour cream until well coated.
Spread the mixture in the prepared baking dish and sprinkle the top with the remaining cheddar. Bake 30 to 40 minutes, until the casserole is bubbly and the cheese is melted.