Serves 6
Do ahead, possibly the day before, possibly weeks before and frozen (in which case you want it thawed):
2 chicken breasts, with bone and skin
Bake at 350F for 45 minutes to an hour. You'll know it's done because the fats have all melted and the skin is nice and crispy and tan. It's a little more rubbery than the even slower roasted at 300 degrees version, but goes a little more quickly, and since you aren't keeping the skin, it doesn't matter. (Another opinion on how to roast these: 
http://simplycooking.wordpress.com/2006/10/22/roasting-chicken/ My method is more like slow roasting, see here: http://www.chowhound.com/topics/333260 )
As an alternative to roasting breasts, use 2 cups of cooked Chicken meat. In either case, shred or dice the meat into 3/4 inch pieces.
Not frozen, but can be done a day or few before:
3/4 cup brown Rice?
1 1/2 cup water
Put in 2 quart saucepan. Bring to boiling, then reduce heat to a simmer. Cover the saucepan and cook for about 45 minutes (rice should be tender and water is absorbed).
An hour before serving
Preheat oven to 375°F. Grease a glass baking dish or casserole (at least 3 quart capacity).
1 tablespoon extra-virgin Olive Oil? 2 cups diced Leek?, white and light green parts only (about 1 large) 1/2 teaspoon salt 1 cup sliced Button Mushroom?s
Heat oil in 3 quart chef's pan or saute pan. Add leek and salt. Cook, stirring often, 2 minutes. Add mushrooms. Cook 2 minutes more. Leek should be softened but not browned.
5 tablespoons brown rice flour
Add flour; stir to coat.
2 cups Chicken Stock? 1 cup Milk? 2 tablespoons dry Sherry? 1/2 teaspoon dried Thyme? 1/2 teaspoon freshly ground Black Pepper?
Add stock, milk, sherry, thyme and pepper and bring to a simmer, stirring constantly.
1 pound Broccoli? florets cut and stem peeled and chopped
OR
2 10-ounce boxes frozen chopped broccoli, thawed
Add broccoli; return to a simmer.
1/2 cup grated Parmesan cheese? 1/4 cup Mayonnaise? 2 teaspoons Dijon Mustard?
Remove from heat and stir in Parmesan, mayonnaise and mustard.
1/2 cup grated Parmesan cheese
In a very large bowl, combine the rice, chicken, and broccoli mixture. Mix to combine, then pour into prepared baking dish. Sprinkle evenly with Parmesan. Bake until bubbling, 20 to 25 minutes. Let cool for 10 minutes before serving.
Source: This is yet another adaptation of the Eating Well Chicken Divan recipe at http://www.eatingwell.com/recipes/chicken_divan.html
I much prefer to roast chicken breasts with the meat and bones still attached. Boiled boneless skinless chicken breasts seem a bit insipid to me. Though it's a perfectly good use of the chicken meat that remains from preparing homemade Chicken Stock, as that had some time cooking with the bones and skin. I thought that there was way too much sauce for the amount of material and it wanted something to sop it up - because it is a very tasty sauce. In fact, just the right amount to create a healthier version of the old Chicken Broccoli Rice casserole that is based on the canned cream of mushroom soup recipe.
Note that your success on reheating broccoli-based dishes will be limited. There is a time limit that it can be heated before it tastes nasty. (http://www.dailyherald.com/story/?id=195688) This dish is OK with the baking, but not with reheating.
Joe's version on noodles: 
http://desertculinary.blogspot.com/2005/06/chicken-divan.html
Historical notes:
From: http://whatscookingamerica.net/History/PoultryDishes.htm
Chicken Divan - A chicken casserole dish with broccoli and mornay or hollandaise sauce.
1950s - Chicken Divan was the signature dish of a 1950s New York restaurant, the Divan Parisienne. In English, the word "divan" came to mean sofa, from the council chamber's benches. In France it meant a meeting place or great hall. It was this meaning that attracted the notice of the owners of the New York restaurant as they searched for a name that would imply continental elegance.
From: http://en.wikipedia.org/wiki/Chicken_Divan
Chicken Divan is a chicken casserole usually served with broccoli, almonds, and Mornay sauce. 1? It was invented at and named for the by-gone Divan Parisien Restaurant in the New York Chatham Hotel. 2?
The Divan Parisien served Chicken Divan as their signature dish in the 1950s. The chef or chefs who originally created it are unknown. In France the word divan refers to a meeting place or great hall. This name was chosen to attract the attention of the Divan Parisien owners by implying a kind of continental elegance.3?
The dish is now commonly prepared with regular parmesan cheese and remains one of the most classic American casserole dishes today. 4?
INSPIRED DISH: Chicken Divan
Los Angeles Times (1886-Current File) - Los Angeles, Calif.
Author: CLEMENTINE PADDLEFORD
Date: Jan 12, 1958
Abstract: In that remote age or the early 20's New Yorkers were introduced to a triumph of a dish uniting chicken and freshly cooked broccoli in a creamy, wonderful way. The creation was named for the restaurant of its origin, Chicken Divan Parisien.
Clearly, wikipedia and whatscookingamerica are a little off in their dating. It may have been famous in the 1950s, but the recipe was developed far earlier. This page, http://www.barrypopik.com/index.php/new_york_city/entry/chicken_divan/
notes that according to a 1938 publication Dining, Wining and Dancing in New York, you could get "Divan Parisien chicken Divan ($1.20)"
Dining in New York By Rian James (1930)
http://books.google.com/books?id=Wgysmzus_1wC&pg=PA124&lpg=PA123&dq=divan+parisien&source=web&ots=7cE9PKMG6x&sig=mbX321741pzdlCRZNXr-4_ACbHY&hl=en#PPA123,M1
starting on page 123 describes the Divan Parisien restaurant, though this publication raves about its Finnan Haddie Mornay with creamed chicory rather than a Chicken and Broccoli Mornay.
Arthur Schwartz (New York City Food, 2004) gives a version quoted here: http://www.relishmag.com/recipes/view/20552/chicken-divan.html
J. J. Schnebel remembers the restaurant and the dish from the 1950s, and gives both an authentic and an easy casserole version: http://members.cox.net/jjschnebel/chdivan.html There's a nice picture of the restaurant on his page.
Adventures in Good Cooking and the Art of Carving in the Home By Duncan Hines,
http://books.google.com/books?id=dqPWqH0gSqYC&pg=PA318&lpg=PA318&dq=divan+parisien&source=web&ots=pCKKlKU0gE&sig=06senaMS9lqbt24T8lNpOEp69HE&hl=en
gives the recipe we know, but its title is "Sliced Turkey, John Paffrath"
(About the book: From the late 1930s, Duncan Hines was known as America's first national food critic and his guidebooks pointed travelers to the best restaurants. Along the way, Hines made countless restaurants famous and began publishing an annual cookbook that brought many of their recipies to the home kitchen. Long out of print, Mercer University Press has proudly revived these culinary classics. 800-637-2378, ext 2880 800-342-0841, ext 2880 www.mupress.org Mercer University Press, 6316 Peake Rd, Macon GA 31210)
From: http://en.wikipedia.org/wiki/Mornay_sauce
A Mornay sauce is a Béchamel sauce with shredded or grated cheese added. Usually, it is half Gruyère and half Parmesan, though variations use different combinations of Gruyère, Emmental cheese, or white cheddar.
It is often served with seafood or vegetables.
Etymology Which duc de Mornay, if any, is honored in sauce Mornay is not usually debated: Philippe, duc de Mornay (1549–1623), Governor of Saumur, and seigneur du Plessis-Marly, writer and diplomat, is generally the favored candidate, but a cheese sauce at his table would have to have been based on what we would term a velouté sauce, for Béchamel had not been invented. Perhaps sauce Mornay is not older than the great Parisian restaurant of the 19th century, Le Grand Véfour in the arcades of the Palais-Royale, where sauce Mornay was introduced 1?. In the tout-Paris of Charles X, the Mornay name was represented by two extremely stylish men, the marquis de Mornay and his brother, styled comte Charles; they figure in Lady Blessington's memoir of a stay in Paris in 1828–29, The Idler in France, (1841). They might also be considered, when an eponym is sought for sauce Mornay.
From: http://www.lisaekus.com/chefadventures/issues/2005/spring/chickendivan.htm
This dish was originally made by folding a half cup of hollandaise into the béchamel sauce. Given that hollandaise is basically butter emulsified with egg yolks, that combination seems unnecessarily rich for today, especially since egg yolks alone give a similar substance to the sauce.
Atomic Can-Opener version
And just to remind you of the processed wonder that this poor recipe turned into when it became the Suburban Housewife special that I remember from my childhood, here's the list of ingredients for a typical Chicken Broccoli Rice casserole:
2 cups water 2 cups uncooked instant rice 2 (10 ounce) cans chunk chicken, drained 1 (10.75 ounce) can condensed cream of mushroom soup 1 (10.75 ounce) can condensed cream of chicken soup 1/4 cup margarine 1 cup milk 1 (16 ounce) package frozen chopped broccoli 1 small white onion, chopped 1 pound processed cheese food (Velveeta) (or alternatively, 16 oz jar Cheez Whiz)
DishCategory?
MethodCategory?:
Fairly Done?
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