1. Preheat oven to 375°F.
2. Cook cauliflower florets in large pot of salted boiling water for 5 minutes; remove and reserve.
3. Melt butter in medium saucepan. Add flour, stirring constantly for 3 minutes on medium-low heat.
4. Pour in milk, whisking to combine, and cook until thickened.
5. Add in cheese and season with salt and pepper. Add more milk if necessary to achieve a smooth consistency.
6. Add in reserved cauliflower and ham. Toss to combine.
7. Lightly grease 9x13-inch baking dish and add cauliflower mixture.
8. Top with chipotle powder and then breadcrumbs.
9. Bake for 20 minutes or until browned and cooked through.
10. Garnish with chopped chives.