Prep

Gather and prepare all ingredients. Preheat the oven to 350°F and grease a 9x9-inch casserole dish with nonstick cooking spray and set it aside.

Pat the chicken dry with paper towels and season evenly with ½ teaspoon of salt and ½ teaspoon of pepper.

Sear

Heat oil in a large skillet over medium-high heat. Once hot, add the cubed chicken in an even layer. Sear in batches if needed.

Drain

Cook undisturbed for 3 minutes, then flip, and cook for another 3 minutes. Remove the chicken from the skillet and place it on paper towels to drain. Set aside.

Melt

Turn the heat to medium and melt 2 Tbsp of butter in the skillet, then sprinkle in the flour and cook for about 1 minute, stirring constantly.

Whisk

Slowly whisk in the chicken broth, whisking until it thickens, for about 1 minute.

Combine

Next, whisk in the milk, remaining salt and pepper, onion powder, and garlic powder. Keep whisking until thick and smooth, for about 2 minutes. Turn off the heat and set aside.

Fold

Place the chicken in a bowl. Pour the sauce, sour cream, and half (1½ teaspoons) of the poppy seeds into the bowl. Fold everything together and place it in the greased casserole dish.

Melt the remaining butter in a medium bowl and add the crushed crackers and remaining poppy seeds to it. Fold together until combined.

Top

Then top the casserole evenly with the poppy-seed buttery crackers.

Bake the casserole, uncovered, in the oven for about 30 minutes until golden brown.