In a shallow bowl, combine the all-purpose flour, garlic powder, onion powder, paprika, salt, and pepper. Mix well.

In another shallow bowl, beat the egg until well combined.

In a third bowl, place the breadcrumbs.

Dip each mushroom slice first into the flour mixture, then into the beaten egg, and finally coat with breadcrumbs. Set aside.

Heat the vegetable oil in a large skillet over medium heat.

Once the oil is shimmering, carefully lay the coated mushroom slices in batches and fry for about 2-3 minutes on each side or until golden brown and crispy.

Using a slotted spoon, remove the mushrooms from the skillet and place them on a paper towel-lined plate to drain excess oil.

In a small bowl, whisk together the mayonnaise, sour cream, ranch seasoning, lemon juice, salt, and pepper until smooth.

Serve the crispy fried mushrooms warm with the ranch sauce on the side for dipping.