In a bowl, mix panko breadcrumbs, Old Bay seasoning, marjoram, garlic powder, and kosher salt. In a separate bowl, pour in the buttermilk for dipping the mushrooms later.

Gently wash and dry your white button mushrooms. Place them in a storage bag with all-purpose flour. Shake the bag to ensure each mushroom is evenly coated.

Dip each flour-coated mushroom into the buttermilk, letting any excess drip off. Roll them in the seasoned panko mixture until fully coated.

In a Dutch oven, pour vegetable oil to a depth of about 1 1/4 inches. Heat the oil until it reaches 375°F.

Carefully add the breaded mushrooms in batches, frying for 2-3 minutes until golden brown. Remove with a slotted spoon and drain on paper towels.

Arrange your crispy fried mushrooms on a platter with your favorite dipping sauce and enjoy!