Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.

Pat boneless, skinless chicken breasts dry. Combine garlic powder, onion powder, paprika, dried Italian herbs, salt, and black pepper. Sprinkle generously over chicken.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Sear seasoned chicken breasts for 4-5 minutes per side until golden-brown.

Transfer seared chicken to an oven-safe skillet or small baking dish. Bake for 15-20 minutes, or until internal temperature reaches 165°F (74°C).

Remove chicken, transfer to a cutting board, cover loosely with foil, and let rest for 5-10 minutes. Shred or dice into bite-sized pieces. Set aside.

Trim cauliflower florets. Use a food processor (pulse in batches until rice-like) or a box grater to rice the cauliflower until uniform in size.

Heat 1 tablespoon olive oil or butter in a large skillet over medium heat. Add riced cauliflower, ¼ cup water (optional), salt, and pepper. Sauté for 7-10 minutes until tender-crisp and most moisture has evaporated.

Optionally, transfer cooked riced cauliflower to a clean kitchen towel, cool slightly, then gently squeeze out any remaining excess liquid.

In a large saucepan or Dutch oven, melt 4 tablespoons unsalted butter over medium heat. Sprinkle in ¼ cup all-purpose flour. Whisk continuously for 1-2 minutes to create a smooth, pale golden roux.

Gradually whisk in 2 cups warmed whole milk and 1 cup warmed chicken broth. Continue whisking until the sauce thickens and becomes smooth and bubbly (3-5 minutes).

Reduce heat to low. Add 8 ounces softened cream cheese, whisking until completely melted and smooth. Stir in Dijon mustard, garlic powder, onion powder, salt, and black pepper. Taste and adjust.

Remove saucepan from heat. Gradually add 1 cup shredded sharp cheddar cheese, ½ cup shredded Monterey Jack cheese, and ¼ cup grated Parmesan cheese. Stir gently until all cheeses are melted and the sauce is smooth and creamy.

In a very large mixing bowl, combine the cooked shredded chicken and the cooked riced cauliflower. Pour about two-thirds of the creamy cheese sauce over the mixture, reserving the remaining one-third.

Gently fold the sauce into the chicken and riced cauliflower until thoroughly coated, being careful not to mash the cauliflower.

Spoon the entire mixture into your prepared 9×13-inch baking dish. Spread it out evenly, pressing gently to create a relatively flat surface.

Drizzle or spread the reserved one-third of cheese sauce evenly over the top. Sprinkle the remaining 1 cup shredded sharp cheddar cheese generously over the surface. Optionally, add cooked, crumbled bacon.

Place the baking dish into the preheated 375°F (190°C) oven. Bake for 25-30 minutes, or until bubbling and the cheese on top is melted, golden brown, and bubbly. If cheese browns too quickly, tent with aluminum foil.

For an extra crispy, golden-brown topping, optionally switch to the broiler setting for the last 2-3 minutes. Watch closely to prevent burning.

Remove from oven and let rest for 10-15 minutes before serving. This allows the casserole to set and flavors to meld.

Garnish with fresh chopped parsley or chives, if desired. Serve warm.