Wipe mushrooms with a damp paper towel or soft brush to remove dirt. Trim the stem ends if dry; leave mushrooms whole if they are 1–1.5 inches. If larger, halve or quarter so they are bite-sized and cook evenly.

Pat mushrooms dry with paper towels. Place them in a bowl and season lightly with 1 tsp coarse salt and 1/2 tsp freshly ground black pepper; toss to coat. Let sit 5 minutes to draw out any excess moisture, then pat dry again.

Breading

Make dry mix

In a shallow bowl or wide plate, whisk together 3/4 cup all-purpose flour, 1/4 cup cornstarch, 1 tsp garlic powder, 1 tsp onion powder, 1 tsp smoked paprika, 1/2 tsp salt, and 1/4 tsp black pepper until evenly combined.

Prepare wet dip

In a second shallow bowl, beat 1 large egg lightly, then whisk in 1/2 cup buttermilk and 1 tsp hot sauce if using. Mix until smooth.

Set up a breading station: mushrooms on a plate, wet bowl, and dry bowl. For extra-crispy mushrooms, you can double-dredge: dip in dry, then wet, then dry again. Otherwise: dredge each mushroom in the dry mix, shake off excess, dip in the wet mix, then press back into the dry mix to coat well. Place coated mushrooms on a wire rack while you heat the oil.

Frying

Heat oil

Pour approximately 1 cup vegetable oil into a heavy skillet (cast-iron or stainless) to reach about 1/2 inch depth, or use a deep pot with 2–3 inches oil for deep frying. Heat oil over medium-high until it reaches 350°F (175°C) or until a pinch of flour sizzles immediately when dropped in.

Fry in batches to avoid overcrowding (3–6 mushrooms per batch depending on pan size). Gently lower coated mushrooms into the hot oil and fry, turning occasionally, until golden brown and crisp, about 3–5 minutes per batch (smaller mushrooms cook faster). Adjust heat to maintain 325–350°F. Use a slotted spoon or spider to transfer mushrooms to a paper towel-lined baking sheet or wire rack to drain.

If you double-dredged, you may need an extra 30–60 seconds per batch to fully cook the interior while crisping the exterior. Sprinkle fried mushrooms immediately with a pinch of salt to taste.

Finishing & Serving

Arrange fried mushrooms on a serving platter. Sprinkle with 2 tbsp chopped fresh parsley and serve with lemon wedges and your choice of dipping sauce (about 1/2 cup). The acid from lemon brightens the flavor; squeeze over mushrooms just before eating.

Leftovers: reheat in a 375°F (190°C) oven on a wire rack for 6–8 minutes to restore crispness. Do not microwave (it will get soggy).