Preheat the oven: Set your oven to 375°F (190°C). Lightly grease a 9x9-inch or similar-sized baking dish.
Cook the bacon: In a skillet over medium heat, cook the bacon until crisp.
Transfer to a paper towel–lined plate and crumble when cool. Reserve 1 tablespoon of bacon fat in the skillet.
Sauté the garlic: In the same skillet, add the butter and minced garlic. Cook for 30–60 seconds until fragrant, stirring constantly so it doesn’t burn.
Build the sauce: Reduce heat to low and whisk in the cream cheese until smooth.
Slowly pour in the heavy cream, whisking to combine. Stir in Dijon, smoked paprika, onion powder, and Parmesan (if using). Season with salt and pepper.
The sauce should be thick but pourable.
Combine with chicken: In a large bowl, toss the cooked chicken with half the cheddar and half the crumbled bacon. Pour the warm sauce over the top and stir to coat evenly.
Assemble the bake: Spread the mixture into the prepared baking dish. Top with the remaining cheddar and the rest of the bacon.
Bake: Place in the oven for 18–22 minutes, until the cheese is melted and the edges are bubbling.
Optional broil: For golden, bubbly cheese, switch to broil for 1–2 minutes.
Watch closely to avoid burning.
Rest and garnish: Let the casserole rest for 5–10 minutes so it sets. Sprinkle with chopped green onions or chives before serving.