Remove stems from portobello, shiitake, and cremini mushrooms. Place stems and mushroom stock in a medium saucepan over medium-high heat; bring to a boil. Reduce heat to low; simmer for 30 minutes. Strain; set aside.
Finely chop portobello cap, and set aside. Thinly slice shiitake and cremini. Place 3 tablespoons butter in a large saute pan over medium heat; add shallots, and cook until translucent, 3 to 5 minutes. Add chopped and sliced mushrooms, and cook until mushrooms are soft and browned, and all liquid has evaporated. Add Marsala, if using, and cook, stirring to loosen any browned bits on the bottom of the pan. Remove from heat, and set aside.
Place the remaining tablespoon butter and flour in a medium saucepan over medium heat; cook until browned and fully combined, 2 to 3 minutes. Slowly whisk in the enriched stock; bring to a boil, whisking until thickened. Add the reserved mushroom mixture and thyme, and stir to combine. Serve hot.
Yes, you can definitely make this ahead. I always make it the day before, and then just pop it on the stove to reheat, stirring occasionally. You may want to have a little stock in the fridge if it gets too thick for you on reheating, but I haven't experienced that.
Does anyone know if this can b made ahead of time?
I've made this a few times already and will be serving it for Thanksgiving this year. My family - all meat eaters except for me - loved this and keep requesting that I make it. I use a mix of dried mushrooms in lieu of using the stems and the broth is quite rich and very woodsy.
This gravy is amazing! I didn't add the wine last year, and it was still delicious. It went fabulously with my Tofurky/veggie meal :} Everybody loved it, I thought it was one of the best recipes I've gotten on here. Definitely going in my recipe tin!