Gather all your ingredients. If your chicken isn’t cooked, poach or roast before shredding into bite-sized pieces. Blanch broccoli florets in boiling water for 2-3 minutes, then transfer to ice water.

In a mixing bowl, combine mayonnaise, sour cream, grated Parmesan, lemon juice, and Dijon mustard. Whisk until creamy and smooth, then add garlic powder, onion powder, salt, and pepper to taste.

Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking dish. Layer shredded chicken at the bottom, followed by the blanched broccoli.

Pour the prepared sauce over the chicken and broccoli, ensuring even coverage. Sprinkle shredded cheddar cheese and breadcrumbs on top.

Bake in the preheated oven for 25-30 minutes until the cheese is melted and bubbly. Let it rest for 5-10 minutes before serving.