Described as "the richest and most delicate potage that can be made and served at a well-ordered table" by  nineteenth century French chef Pierre Blot, potage à la reine is a creamy soup made with chicken and almonds that originated as a sort of a savory blancmange. 
Translated into English as “in the Queen’s style,” the phrase “à la reine” has come to indicate a recipe with chicken as its main ingredient, just as dishes with “a la king” in the title represent chicken dishes in America. The dish was given the title “potage à la reine” during the Renaissance era, although there are conflicting reports about which Queen is the soup’s namesake.
Although attribution has been given to both Mary Queen of Scots and England’s Queen Victoria, the most commonly held legend links the dish to Queen Marguerite, wife of King Henry IV of France and daughter of Catherine de Medici of Italy and Henry II. Potage à la reine was the “Thursday’s soup” at the Court of the Valois, and the name is said to derive from the fact that Queen Marguerite was extremely fond of it. 
A multi-layered soup with a distinctive look and taste, the original version of potage à la reine cleverly fused a meat stock derived from poultry (and sometimes veal or beef) with rich almond milk. The almonds give the potage its characteristic whitish color - the use of dairy products or rice to provide a creamy look and feel were substituted much later. In addition to adding depth, texture and flavor, the light color was also a status symbol.  On royal tables, the Queen was always given the choicest, most tender white meat of the chicken since foods that were light or white in color were considered superior.     
I first learned about this soup doing research for my book, The Thousand Dollar Dinner. It really intrigued me - especially the use of almonds as a thickener and flavoring -  so I set out to try to recreate it. There are many different versions of this dish ... the older versions are extremely involved, with the combination of meat-based and  chicken stocks, and almond milk made by steeping the almonds and pounding them in a mortar. I decided to merge components from two recipes: one from Jacques Pepin and one from a website called Coquinaria, which features historical recipes (mostly Medieval) tested by Christianne Muusers, who is Dutch. I didn't want to have to deal with making a meat stock, so I just used one that was chicken-based, but I did make my own almond milk, which was admittedly easier with today's modern tools, such as the blender I used to make breadcrumbs and grind the almonds. But wow - it made such a difference. What a unique, delicate flavor - better than any other chicken soup I have ever tasted. It was still a lengthy process, but well worth it if you have the time. Here's what I did:

Potage à la reine 

Ingredients:

• 2 poussins (you could also use Cornish hens or one 2 1/2 to 3 pound chicken)
• Salt and pepper
• Melted butter
• Bacon
• 1 tbsp herbs de Provence
• 1 large onion, peeled and cut into 4 pieces
• 12 whole cloves
• 1 tsp fennel seed
• 1 tbsp dark soy sauce
• Bouquet garni: parsley, chives and thyme
• 1/4 lemon (only pulp, no peel or white)
• 1 1/4 cup ground almonds
• crumbs of two slices of white bread

Garnishes:

• 1 leek, (root end and leaves removed), remainder julienned
• 3 carrots, peeled and julienned
• 2 ribs celery, peeled and  julienned
• 6 large mushrooms, thinly sliced
• Pistachios (shelled)
• Pomegranate seeds

Directions:
Sprinkle the poussins with salt and pepper and put them in a roasting pan breast side up. Baste with melted butter, and cover them with slices of bacon. Roast for 50 minutes in a preheated oven (350 F), basting often. Remove the bacon ten minutes before the end of the roasting time. When done, remove the poussins from the oven and let them rest for fifteen minutes before deboning. Keep meat and bones apart.
Make a stock by placing the poussin bones in 6 quarts lukewarm water - bring to a boil over high heat. Reduce heat and boil gently for 30 minutes. Most of the fat and impurities will rise to the surface - skim off and discard as much as possible. Add herbs de Provence, onion, cloves, fennel seed and soy sauce, return liquid to a boil over high heat. Reduce heat and boil gently for 2 hours. Strain through a fine-meshed sieve or cheesecloth. Allow stock to cool and then remove surface fat.
To make the almond stock, place half the chicken stock, bouquet garni, lemon, ground almonds and  bread crumbs in a pot and bring to a boil. Let simmer for 20 minutes, stirring frequently. Strain though a fine-meshed sieve or cheesecloth, squeezing the pulp to get as much liquid as possible. 
 Just before serving, combine the two broths and add the vegetable garnishes with their cooking juices and the shredded chicken. Reheat gently to a boil and simmer for 5 minutes.
After ladling into bowls, additional garnishes of pistachios  and pomegranate seeds can be added if desired.
Enjoy!

Sources: 
Potage à la Reine - The French origins of a Dutch soup, Coquinaria
Potage A La Reine By JACQUES PEPIN, The New York Times ( Originally published with Food; Soup, Beautiful Soup, March 31, 1991).