Roast diced mushrooms on medium-high heat until golden brown in canola oil (or any cooking oil you prefer.)

Remove from pan, turn the heat down to low medium and sweat (gently cook without browning) onions and celery in the same fat.

Add mushrooms back in and continue to cook until there is no residual moisture in the pan (about 3-4 min depending on pan temperature; this may go quicker or slower depending on how roasted the mushrooms are).

Remove from heat and add in marsala.

Remove from pan as soon as marsala comes to a simmer, cool and store in the fridge, then season with salt to taste.

To finish this for serving, add about 100 ml of cream, and allow to reduce by half, re-season as necessary, then add fresh cooked pasta and toss together.