Chicken Broccoli Casserole

Preheat oven to 400ºF.

Heat butter in a large cast iron skillet over medium-high heat. Add onions and 1/2 tsp salt and stir. When onions soften (about 6 minutes), add the garlic and cook a minute more.

Sprinkle flour over the onions and stir. Whisk in the broth, 1/2 cup at a time to prevent lumps. Allow mixture to come to a boil and thicken up.

Once the sauce is bubbly and thick, turn off the heat. Whisk in the sour cream, mayo and black pepper. Taste and add more salt to taste (see recipe note below).

Gently stir in the broccoli, chicken and rice. Top with cheese.

Drizzle olive oil over breadcrumbs in a small bowl and use your fingers to combine until all the breadcrumbs are moistened. Sprinkle over cheese. Bake until bubbly and golden, about 20 minutes.