You say Portobello, I say Portabella. Either way tastes delicious, especially grilled with herbed goat cheese and grilled red onions. How's that for Meatless Monday (or any day)? This recipe comes from Williams Sonoma, specifically from their "What's for Dinner? Burger Night Cookbook" (see last link below).
The "before" pictures comes from Far West Fungi, a family-run, certified-organic "cultivator of edible/medicinal mushrooms, & wild forest products," with consumer presences in the SF ferry building & farmer's markets."
Ingredients listed here, but see the first link to the full recipe on the Williams Sonoma website. The second two links are to the Far West Fungi website and Instagram respectively.