Start by wiping the mushrooms well with a paper towel or kitchen towel. Trim any woody or soft ends off, and cut larger mushrooms into halves or quarters.

In a bowl, mix together the all-purpose flour along with salt, garlic powder, onion powder, sweet paprika, and black pepper. Toss the cleaned mushrooms in about a quarter of this flour mixture.

In another bowl, combine soda water (or beef broth), buttermilk, and egg. Whisk until well blended. Sift in the remaining flour mixture and stir gently until combined.

Pour panko breadcrumbs into another bowl and arrange it next to your batter bowl and flour-coated mushrooms. Heat enough oil in a large saucepan until it reaches about 350ºF (175ºC).

Take each mushroom and dip it first into the batter, allowing excess to drip off before dredging in panko breadcrumbs. Place them aside on a plate.

Fry each mushroom for around three to five minutes until golden brown and crisp, stirring occasionally for even cooking.

Transfer the fried mushrooms onto a tray lined with paper towels to absorb excess oil. Serve immediately.