Prepare the Mushrooms:

1. Slice the Mushrooms: Clean the mushrooms with a damp paper towel and slice them into ¼-inch thick pieces. Set aside.
2. Set Up the Dipping Stations: In a shallow bowl, whisk together the flour, garlic powder, onion powder, paprika, salt, and pepper. In a separate bowl, whisk the egg and buttermilk together until well combined. In a third bowl, add the panko breadcrumbs.

Coat the Mushrooms:

3. Dip in Flour Mixture: Take each mushroom slice and dip it into the flour mixture, making sure it’s fully coated. Shake off any excess flour.
4. Dip in Egg Mixture: Next, dip the floured mushroom slice into the egg and buttermilk mixture, ensuring it’s fully submerged.
5. Coat with Panko: Finally, dredge the mushroom in the panko breadcrumbs, pressing gently to ensure an even coating. Repeat with the remaining mushroom slices.

Fry the Mushrooms:

6. Heat the Oil: In a large skillet or frying pan, heat the vegetable oil over medium-high heat until it reaches 350°F (175°C). Use a thermometer to check the temperature, as the oil should be hot but not smoking.
7. Fry the Mushrooms: Working in batches, carefully place the coated mushroom slices into the hot oil. Fry for 3-4 minutes per side, or until golden brown and crispy.
8. Drain the Mushrooms: Use a slotted spoon to remove the mushrooms from the oil and place them on a paper towel-lined plate to drain excess oil.

Serve the Mushrooms:

9. Prepare the Ranch Dipping Sauce: Serve the fried mushrooms with a side of ranch dressing for dipping. If desired, sprinkle with additional salt and pepper for extra seasoning.