1 large head cauliflower, cut into small florets (1.5 lb. florets)
2 tablespoons olive oil
1 teaspoon coarse kosher salt (not fine salt)
1/4 teaspoon black pepper
1/2 cup full fat sour cream
2 tablespoons whole milk
1 teaspoon Dijon mustard
1 teaspoon minced garlic
Pinch of pepper
1 cup shredded sharp cheddar, divided
2 tablespoons bacon bits
2 tablespoons thinly sliced scallions, green parts
Preheat oven to 425 degrees F. Line a rimmed baking sheet with parchment paper.
Arrange the cauliflower florets on the baking sheet. Toss with olive oil and season with kosher salt and black pepper.
Roast the cauliflower until tender-crisp, about 12 minutes.
Meanwhile, in a large bowl, mix the sour cream, milk, Dijon, garlic, pepper and 1/2 cup cheddar.
When cauliflower is done, add it to the sour cream sauce and mix to combine.
Transfer the mixture to a greased 1.5-quart baking dish. Top with the remaining shredded cheddar.
Return to the oven and bake just until cheese is melted, about 10 minutes.
Sprinkle the cauliflower casserole with the bacon bits and the scallions and serve.