Madeira Sauce

Note that this calls for 4 C of Mushroom Essence, and also note that it involves a double reduction and fairly extensive cooking time.  It's pretty heavenly, though, so if you have some free time in the afternoon, you should make some.

1 Tbsp olive oil
1 yellow onion, thinly sliced
6 cloves garlic, chopped
salt
1/2 pound button mushrooms, sliced
1 Tbsp tomato paste
2.5 cups red wine (note: this is most of a full bottle)
8-10 fresh thyme leaves (I added ~1 tsp dried Thyme)
10-12 parsley sprigs with stems (I didn't have this, so I didn't add it)
1 bay leaf
6 whole peppercornses
4 C Mushroom Essence
3 Tbsp unsalted butter
3 Tbsp all-purpose flour
1/2 C Madeira wine*
Freshly ground pepper

Heat the olive oil over medium heat, then add the onion and saute until soft and translucent (~10 minutes).  Then add the garlic and a pinch of salt and saute until the onion starts to turn brown and soft (another ~5 mins).  Add the mushrooms and cook, stirring and scraping the bottom of the pan, until the mushrooms are browned (5 mins more).

Now add the tomato paste, continuing to stir and scrape, and then add the red wine, thyme, parsley, bay leaf, and peppercornses.  Now it's time for the first reduction.  Cook at a low boil until the sauce has been reduced by one quarter (3 C; will take ~15 mins).  Then add the mushroom essence and cook at a low boil again until reduced by one-quarter yet again (~5.5 cups, another 15 mins).  Reduction 2.

While that's happening, make a roux: In a small skillet, melt the butter over medium heat, add the flour, and stir until the mixture is light brown and mildly toasty.

Now, add the Madeira to the twice-reduced main broth, lower the heat, and simmer another 10 minutes.  Then remove from heat and pour the sauce through a metal mesh strainer, pressing the solids to extract as much of the delicious juices as possible.  Discard the solids, perhaps by feeding them to a worm bin.

Return the broth to a pan, add the roux, and bring the strained sauce to a boil until all lumps disappear and the sauce begins to thicken.  Season with salt and pepper and keep warm over low heat.

*I couldn't find any Madeira wine, after searching high and low at the local grocery store.  So I wound up using some tempranillo that had been sitting around for a while, plus some cabernet sauvignon.  From what I've read about Madeira wine, it is often somewhat spiced, so it probably contributes some nice flavor.  It originates from Portugal and can vary considerably in its characteristics.