Pat mushrooms completely dry. Trim stems if needed and set aside.
Set up three bowls: flour with a pinch of salt and pepper; eggs whisked with water; breadcrumbs mixed with Parmesan, garlic powder, onion powder, parsley, paprika, remaining salt, and pepper.
Dredge mushrooms in flour, shaking off excess. Dip in egg, then coat in breadcrumb mixture, pressing to adhere.
Rest breaded mushrooms on a rack or sheet for 5–10 minutes to help the coating set.
Heat about 1/4 inch oil in a large skillet over medium-high until shimmering (around 350°F).
Fry mushrooms in batches, turning until deep golden and crisp, 3–4 minutes total. Transfer to a rack and lightly salt.
Sprinkle with fresh parsley and serve hot with your favorite dipping sauce.