Disclaimers:
1) The original Duxelles recipe I got from James Beard's cookbook, but this is my version of it. 2) this isn't really canning and preserves, but I wasn't sure which subcategory to use and it is all about freezing for later use.

Intro:
Duxelles is basically just minced mushrooms sautéed in butter and frozen or refrigerated for later use. Those later uses include in omelettes, stews, soups, and anything else that you think would be better with a little sautéed mushrooms. Ramps, for those of you who don't know, are a wild edible in the garlic family, available in the spring. I get mine at my local farmers market. This time, I used crimini mushrooms, but specials (white, button) or portobello work fine too. I haven't tried it with shiitake or oyster, etc., but I see no reason why they wouldn't work also.

I freeze the duxelles in an ice cube tray, then store the cubes in the freezer in a ziplock type bag. Once the tray is full, any extra goes in a plastic container in the fridge, where it will stay good for two weeks or so.

Apology: I didn't think to do the instructable until I had finished the first two batches, so I have no pictures with the ice cube tray empty. The first six in the tray were plain, the second six had spring garlic instead of ramps..

Variations:
Substitute spring or regular garlic, fresh chives, or onions, add a splash of red or white wine, or add a little grated nutmeg or a sprinkle of tarragon leaves while cooking. Feel free to experiment, and let me know how it goes!

Ingredients:
Fresh mushrooms (3 largish crimini will fill 6 ice cube compartments in the tray, so to fill a whole tray, use 8 large, or 10-12 smaller)
Butter (you can use olive oil or margarine, but it won't taste as good or freeze as well) I use unsalted by choice, but salted is fine.
Ramps about 3 seems right. You can include the leaves, or set them aside to add to a salad, or wrap around a bite of soft stinky cheese (YUM!)

Tools:
Cutting board
chopping knife
Sautéing pan ( I like a small cast iron, but any low, stovetop will do)
Stirring spoon
Ice cube tray
Tablespoon

Step 1: Prepping

Don't wash mushrooms! Wipe them off with a damp paper towel, or use a natural bristled brush to gently brush off any loam ( I use a 1/2" trim painting brush from the hardware store for that, and as a basting/pastry brush - cheaper than a fancy pastry brush and works just as well - just don't use one that's been used to paint!)

Wash the ramps well in cold water.

Put about two tablespoons of butter in the pan ready to melt.

Step 2: Chopping It Up

Slice and dice the mushrooms, then chop up fairly small or mince. I don't recommend going larger than the final mushroom chopping picture. I suppose you could use a blender or food processor, but I find I lose a lot that way, and it doesn't take long. Don't bother removing the stems from the mushrooms, they can be used in this. Set aside in a bowl to give yourself room on the cutting board.

Trim the roots off the ramps, Slice, then chop up to mince. You will notice I didn't use the leaves, that was because I had used them in a salad previously. It's fine and tasty to use the leaves too in this.

Turn the heat under the pan to a medium flame, and melt the butter, then spread it around the pan bottom DO NOT BURN.

Step 3: Cooking

Ramps take a little longer than mushrooms to cook, so I add them first, stirring lightly until they just start to get translucent, or start to sizzle a bit.

TURN DOWN THE HEAT you want the flame low now.

Add the mushrooms and stir a bit to mix the ramps in well. Stir occasionally until they start to give up their juices and change color. Be careful not to overcook and so lose the juices! You will notice that when you add the mushrooms, they will soak up all the butter, then start to change color and get juicy again, that's exactly what they should do. You may hear slight sizzling at first, if it continues, turn down the flame a bit. You want them juicy, and looking lightly cooked, not dry and dark brown or fried. When done, turn off flame. The whole cooking time from adding the ramps should be maybe 7 or 8 minutes, although I did not time it.

NOTE: James Beard cooks his longer, using more butter at a simmer, until the mushroom juices are nearly all gone and the 'shrooms are quite dark and nearly a paste. I like it both ways.

Step 4: Storing

Use a tablespoon sized measuring spoon ( or similar) to spoon the Duxelles into the clean, dry ice cube tray. Any spoon would work, but each cube holds about a heaping tablespoon.

If there are any juices left, pour over the Duxelles in the tray.

Set aside to cool before freezing.

If you have more duxelles than tray room, store in an airtight container in either fridge or freezer after it has cooled off.

Once the duxelles have frozen ( I usually give it 3-4 hours) empty tray onto a sheet of wax paper, store cubes of duxelles in a Baggie or other airtight container in the freezer.

After preparing, duxelles will keep in the fridge two to three weeks, or in the freezer for two or three months.

Step 5: Using

Refrigerated duxelles can be used as a filling for an omelet, crepe, tart, dumpling, as a spread on toast, stirred into hot pasta, as a base for a dip, add to ground beef for hamburgers or meatloaf, or any of things listed under frozen, except deglazing.

Frozen duxelles can be added as is to a stew, soup, gravy, or a sauce, while they are cooking, it can be added to the pan while still hot after cooking meat to help deglaze the pan,

To thaw the frozen cubes, place in a bowl or other container in the fridge for 24 hours.

The image is angel hair pasta with duxelles, sautéed asparagus, and a little cheese.