Prepare the batter: In a shallow bowl, combine flour, cornmeal, garlic powder, salt, pepper, and paprika. In another bowl, whisk together the egg and buttermilk.
Coat the mushrooms: Dip each mushroom into the egg mixture, then dredge it in the flour mixture, ensuring it's well coated.
Fry the mushrooms: Heat vegetable oil in a large skillet over medium-high heat. Fry the mushrooms in batches for about 3-4 minutes, or until golden brown and crispy. Remove with a slotted spoon and drain on paper towels.
Make the herb dipping sauce: In a small bowl, combine sour cream, mayonnaise, dill, parsley, lemon juice, garlic powder, salt, and pepper. Stir well to combine.
Serve: Arrange the fried mushrooms on a platter with the herb dipping sauce on the side for dipping.