Instructions

  1. Preheat oven to 375.
  2. Steam cauliflower until crisp-tender, about 9 minutes.
  3. Transfer to 13x9x2"-inch glass baking dish.
  4. Melt 3 tablespoons butter in heavy large saucepan over medium heat.
  5. Add flour and stir 2 minutes (do not brown).
  6. Gradually whisk in half and half.
  7. Cook until sauce boils and thickens, whisking constantly, about 4 minutes.
  8. Mix in 5 tablespoons horseradish and vinegar.
  9. Season to taste with nutmeg, salt and pepper.
  10. Pour sauce over cauliflower and mix to coat.
  11. Sprinkle cheese over.
  12. (Can be made 1 day ahead. Cover and chill).
  13. Melt 3 tablespoons butter in heavy medium skillet over medium heat.
  14. Mix in mustard and remaining 2 tablespoons horseradish.
  15. Add breadcrumbs; stir until crumbs are golden brown, about 9 minutes.
  16. Sprinkle over cauliflower.
  17. Bake until cauliflower is heated through, about 25 minutes.