Step 1

For the sauce: Combine the milk and broth in a large, heat-safe measuring cup. Microwave on MEDIUM just long enough to warm through (without boiling).

Step 2

Melt the butter in a medium, heavy saucepan over medium heat. Whisk in the rice flour and cook for 2 minutes, whisking constantly. Slowly pour in the warm milk-broth mixture, whisking, until all of the liquid is incorporated. Stir in the cheese; cook for 4 to 5 minutes, whisking to form a smooth sauce that has thickened enough to coat the back of a spoon. Season with salt and pepper to taste. The yield is 2 cups.

Step 3

For the casserole: Combine the butter and oil in a medium skillet over medium heat. Once the butter has melted, add the onion and garlic; cook for about 6 minutes, stirring occasionally, until the onion is soft. Add the rice and stir to coat evenly.

Step 4

Combine the 2 cups of sauce, the sour cream, lemon juice and broth in a large bowl; mix well, then add the rice mixture, chicken and spinach, stirring to incorporate. Season with salt and pepper to taste.

Step 5

Preheat the oven to 350 degrees. Use nonstick cooking oil spray to grease the inside of a 9-by-9-inch baking dish.

Step 6

Spread the chicken-rice mixture evenly in the baking dish. Cover with aluminum foil and bake for 35 minutes. If you plan to serve the casserole right away, uncover and sprinkle the bread crumbs evenly over the top. Broil for 3 to 5 minutes or until the the crumbs have lightly browned.

Step 7

If you plan to freeze the casserole, bypass the bread crumb step. Remove the casserole from the oven after the 30 minutes and allow it to cool. Cover with plastic wrap and refrigerate to chill through. (At this point, if desired, cut it into individual portions and wrap each one first in plastic wrap, then in foil.) Freeze for 6 to 8 hours, then unmold and wrap first in plastic wrap, then in foil. Return to the freezer and store for up to 6 weeks.