For the crispy parmesan mushrooms, create a dredging station. In one shallow bowl, whisk together the flour, water, 1 teaspoon salt, and ½ teaspoon pepper until fully combined. The batter should be quite thick – enough to coat the back of a spoon – if it’s too thick, add 1-2 tablespoons of water at a time, until you reach the right consistency.
In a second bowl, mix the parmesan, breadcrumbs, 1 teaspoon salt, and ½ teaspoon pepper until thoroughly combined.
Working in batches, toss the mushrooms in the flour batter, ensuring they’re fully coated. Using a slotted spoon, tap off any excess batter, then place the battered mushrooms in the parmesan breadcrumb mixture, tossing to coat. Repeat until all the mushrooms are battered and coated.
Heat the oil in a large sauté pan over medium heat – the oil should be about ½ – inch deep. Working in batches, fry the mushrooms until golden and crispy, 5 to 7 minutes. Transfer to a wire rack or paper-towel lined plate and repeat with the remaining mushrooms.
Meanwhile, prepare the arugula pesto. Place all its ingredients, starting with only ¼ cup of water, into a blender and pulse until smooth, adding more water if you want a runnier consistency. Set aside.
To build the tacos, spread some pesto on the bottom of a warmed tortilla. Top with a small handful of mixed greens, followed by a few parmesan crusted mushrooms. Garnish with vegan feta, picked onion, and microgreens. Serve with fresh lemon wedges, and enjoy!