To make the sauce, add the cream cheese and cream to a pot and warm it slowly, stirring frequently, over low heat. When combined, add the mustard powder and garlic. Remove from the heat and stir in the shredded cheese blend, crisp-cooked bacon, and green onions. Set aside.

Prepare the cauliflower by breaking the head into bite-size florets, cutting them in quarters if necessary. Remove excess stems. Rinse and shake to dry.

Put the cauliflower into a large bowl and add about half the cheese sauce. Stir well to combine. You want it saucy but not drowning in sauce, so add more if needed. 

Put the cheesy cauliflower into a baking dish or individual ramekins and bake in a 375-F oven for about 20 minutes. Individual size dishes will require much less cooking time, maybe 8-10 minutes, so check frequently. You want the top to be bubbly and brown and the cauliflower tender-crisp.