Start by wiping the mushrooms gently with a paper towel to remove dirt, ensuring they are dry for optimal frying. Trim any woody stems and slice larger mushrooms to approximately the same size, about a quarter, for uniform cooking.

In a mixing bowl, whisk together the all-purpose flour, salt, garlic powder, onion powder, paprika, and black pepper until well blended. In another bowl, combine the carbonated water or beer, buttermilk, and egg, mixing until smooth. Gently fold in the flour mixture until just combined.

Prepare your breading station by placing the bowl of Panko breadcrumbs next to your batter and a separate plate for the coated mushrooms.

Pour vegetable or canola oil into a deep saucepan, filling it 3-4 inches deep, and heat the oil to 350°F (175°C).

Take each mushroom and dip it into the batter, allowing any excess to drip off. Immediately roll it in the Panko breadcrumbs.

Carefully place the coated mushrooms into the hot oil in batches, frying them for 3-5 minutes until golden brown.

Once golden and crispy, use a slotted spoon to transfer the fried mushrooms to a paper towel-lined tray, allowing any excess oil to drain. Serve hot, garnished with fresh parsley.