Step 1: In a large bowl mix flour, baking powder and salt. Add water and mix until a smooth batter has formed. Dip mushrooms into the batter and coat evenly. Allow excess batter to drip off.
Step 2: Roll the mushrooms in breadcrumbs until coated thoroughly. Repeat until all mushrooms are coated.
Step 3: Heat deep fryer to 365 degrees. Deep fry mushrooms in batches until golden brown. Drain on paper towels.