Preheat the oven to 350°F (175°C). Lightly grease a 9×13-inch casserole dish.

Cook the bacon in a large skillet over medium heat until crisp, approximately 8 to 10 minutes. Transfer it to a paper towel-lined plate. Once cool enough to handle, crumble or chop it. Reserve approximately 2 tablespoons for the top.

Cut the cauliflower into evenly sized florets. Steam for 5 to 7 minutes, or until just fork-tender but not completely soft.

Drain the cauliflower thoroughly, then return it to the warm pot for 2 to 3 minutes. This allows the remaining moisture to evaporate and helps prevent the casserole from becoming watery.

Melt the butter in a skillet over medium heat. Add the garlic and cook for about 30 seconds, just until fragrant.

Stir in the heavy cream and water or broth. Bring the mixture to a gentle simmer, then reduce the heat to low.

Add the softened cream cheese and whisk until completely smooth. Remove the skillet from the heat, then gradually stir in 1 cup of shredded cheddar until melted. Season with salt and black pepper. Taste the sauce before adding more salt because the bacon, cheddar, and broth may already be salty.

Transfer the drained cauliflower to the prepared casserole dish. Pour the cheese sauce over the florets. Add the bacon and 2 tablespoons of green onions, then stir gently until the cauliflower is evenly coated.

Sprinkle the remaining ½ cup of cheddar over the casserole.

Bake uncovered for 20 to 25 minutes, or until the sauce is bubbling around the edges and the cheese has melted.

Let the casserole rest for 5 minutes. Finish with the reserved bacon and remaining green onion before serving.