For those who aren't familiar with the term, a Supreme sauce is an incredibly rich sauce traditionally based on chicken velouté that is terrific on roasted chicken or even pork. A bit time consuming but the WOW factor is huge if done properly. It's sort of a very upscale country gravy in a way.
The recipe is in the extended entry.
Here's how I like to make it at home, this makes about a pint of Supreme, which is enough for a 1/2C portion for 4 people, scale how much you make depending on how decadent you want to be with the portions and if you want it over your vegetables, too:
To make the velouté, which is one of the 5 mother sauces:
1 Q plus a pint of high quality chicken stock. If you can't use home-made, use a good low or no salt broth because this is going to reduce a lot so it can become quite salty. The extra pint is to compensate for evaporation.
2 oz. flour (about 1/2 C, though it's a good idea to weigh it.)
2 oz. unsalted butter (1/2 a stick. Only have salted? See above and be warned.)
Get your stock into a stockpot and bring it to a simmer if it's cold.
In a skillet with rounded sides on medium heat, get your butter melted, then add your flour to create a roux. Keep stirring/whisking it until turns an ivory color and starts to smell like cookies. Gradually deglaze with some of your stock until it's incorporated and in no danger of clumping, then add your deglazed roux to your stock pot. Stir and simmer until the sauce has reduced a bit so you end up with a quart of sauce.
For the Supreme Sauce:
2T of unsalted butter, ideally clarified but not required
2T of shallots, minced
1/4C white wine
1/2C heavy cream
1Q Chicken Velouté
Kosher salt and pepper (use white pepper if you don't want the specks)
1/2 a lemon or so
2T cold butter, whole
Okay, here we go. Bring your velouté to a simmer. Sweat your shallots in the clarified butter until softened but not browned. Deglaze with the white wine and simmer until nearly dry (this is called au sec, if you see this term anywhere). Add the cream and reduce until it coats the back of a spoon. (This is called nappé, if you dip a spoon in your sauce and turn it sideways, you should be able to draw a line through it with your finger and have it maintain its shape.)
Add your shallot/cream mix to your now warm velouté and reduce GENTLY about 50% to around the nappé state. TASTE! Season. If you've used canned broth it may need no salt at all, add pepper to taste and a squirt of lemon juice will perk up the sauce, use your judgement.
If it's ready, remove it from the heat and whisk in your 2T of cold butter.
This gave me a chuckle. I skimmed the recipe and couldn't figure out what the Chicken Veloute was. Why would that be? One of the first things my mother taught me to cook was gravy. Roux + chicken stock+ stir like the dickens = gravy. So when I saw the first part of the recipe my brain immediately said "gravy" so I just couldn't figure out what you'd done with it or what in the world Veloute was. There ya go.
Oh! And Swanson's Natural Goodness is an excellent chicken stock. I tried Better than Bullion for a while but Natural Goodness is better.