About the Recipe
Duxelle is rich in flavor and can be used as a spread in a wide variety of hors d’oeuvres and is commonly used in Wellingtons. This recipe makes enough Duxelle for 4 Chicken or Beef Wellingtons. If you just want to make a bit of spread for hors-d’oeuvres, cut the recipe in half.
I like using Mini Bella mushrooms because of their rich flavor. However, you can use common white mushrooms or any other mushroom, if you prefer.

Ingredients
1360 grams (48 Oz) of Mini Bella mushrooms
¼ cup of butter
½ cup of dry red wine
1-2 shallots
2 cloves of finely chopped garlic
¼ teaspoon of ground black pepper
¼ teaspoon of salt
Preparation
Preparing the Mushrooms
Put the mushrooms in a large colander and rinse them well.
Rinse every mushroom individually to ensure there is no residual soil.
Since the mushrooms will be liquefied and cooked immediately, washing them is not an issue.
Cut off any unsightly stem ends.

Chop the mushrooms into pieces.

Use a full sized food processor with a cutting blade to puree the mushrooms.
Start by filling the food processor basket.
There will be too many mushrooms for you put them all in the food processor at once, unless you have a huge food processor.

Cover the food processor and put it on high speed.

The pureeing process will make the mushrooms take up much less space in the processor basket.
Continue adding the remaining mushrooms as the contents of the basket reduce.
You can add the shallots anytime during this process.
Throughout the initial process, you will frequently have to stop the food processor and redistribute the mushroom mix for it to continue chopping. Otherwise, the spinning blade creates an empty space in the middle of the mix and the chopping process stops. Press down into the mushrooms with a spatula (with the processor powered off) to redirect the mushrooms towards the blade and then resume the processing.

Eventually, the mix will liquefy and it will become easier to process.
Continue to puree the mushrooms until there are no discernable pieces and it is the consistency of apple sauce.
Mushroom Cooking Process
Put the butter and garlic in a large non-stick pan and set temperature to low, or simmer.

Add:
The mushroom puree
The dry red wine
Salt and pepper
It's a good idea to put a cover on the pan for the first hour or more of the cooking process. Otherwise, there will be a lot of splashing when the puree begins to boil and you will make a mess of your stove.
Continue cooking, stirring periodically.
Once a significant amount of the water has boiled off, the splashing hazard will no longer be an issue and the remainder of the cooking process can be done without a cover. This should take about 1 and 15 minutes. At this point in time, you can increase the temperature to medium-low.
It will take 2 ½ to 3 hours or more of cooking before the Duxelle has dried sufficiently. Cook it until it has the consistency resembling cooked ground beef.
You should not see any liquid ooze out when you press it to the bottom of the pan with a spatula. A Duxelle that is too moist will make your puff pastry soggy when you cook your Wellingtons.
Pack the mixture into the bottom of a bowl to bind it all together and let it cool to room temperature. Then, refrigerate for 2 hours or so before using it.

As you can see, there is not much left in the end. If you use ½ cup of Duxelle per Wellington, this recipe makes enough for 4 Wellingtons. One Wellington typically serves 2 people so this recipe makes enough to serve 8.