Clean mushrooms by wiping with a damp paper towel or a soft brush. Trim any tough stems; leave small mushrooms whole and halve larger ones so pieces are roughly uniform in size (about 1–1.5 inches). Pat dry thoroughly with paper towels.

Season dredge flour

In a shallow bowl or plate combine 1 cup all-purpose flour (for dredging), cornmeal (if using), 1 tsp salt, 1/2 tsp black pepper, 1/2 tsp garlic powder and 1/2 tsp paprika. Toss briefly to blend.

Make wet batter

In a medium bowl whisk together 2 eggs and 1/2 cup buttermilk until smooth. Add 3/4 cup flour, 1/4 cup cornstarch, 1/2 tsp baking powder, 1 tsp hot sauce (optional) and a pinch (1/4 tsp) of salt. Slowly whisk in 3/4 cup cold sparkling water or beer until the batter is smooth and thick but pourable — like a heavy pancake batter. Keep batter cold (set bowl in a larger bowl with ice if hot kitchen).

Set up dredging station

Arrange three stations: seasoned dry dredge (flour mixture), wet batter, and a wire rack lined with a baking sheet for finished pieces. Pat mushrooms again if any moisture remains.

Dredge the mushrooms

Working in batches, toss mushrooms in the dry dredge to coat lightly, shake off excess, then dip into the wet batter ensuring full coverage. Let excess batter drip off for 5–10 seconds and place on the wire rack. Repeat until all mushrooms are coated. Return any wet hands to flour to avoid sticky handling.

Heat oil

Pour vegetable oil into a large heavy-bottomed skillet or Dutch oven to a depth of about 1 to 1.5 inches (roughly 1 cup may be enough for a small pan; increase if using a larger pot). Heat over medium-high until oil reaches 350°F (175°C). If you don't have a thermometer, test with a small drop of batter — it should sizzle and rise steadily without burning immediately.

Fry the mushrooms

Carefully add 4–6 battered mushrooms to the hot oil in a single layer, do not crowd. Fry for 2.5–4 minutes, turning once with tongs, until golden brown and crisp. Smaller mushrooms may cook faster; larger ones may need a little longer. Adjust heat to keep oil at 325–350°F (160–175°C) so the exterior browns evenly without burning.

Drain and finish

Use a slotted spoon or spider to transfer fried mushrooms to a paper towel–lined baking sheet or wire rack to drain. Immediately sprinkle with a pinch of salt. Repeat frying remaining mushrooms in batches, letting oil return to temperature between batches.

Serve

Arrange fried mushrooms on a serving platter, sprinkle with chopped fresh parsley. Serve hot with the dipping sauce or your favorite condiments.

Dipping Sauce (optional)

While frying or up to a few hours ahead, whisk together 1/2 cup mayonnaise, 1/4 cup sour cream or Greek yogurt, 1 tsp lemon juice, 1 tsp Dijon mustard and 1/2 tsp minced garlic until smooth. Season with 1/4 tsp salt and 1/4 tsp black pepper. Taste and adjust acidity or seasoning. Transfer to a small bowl and chill. Sprinkle a little paprika on top for color before serving.