Sift flour, kirmizi biber, salt, sugar and baking powder into a bowl. Slowly whisk in beer making sure there are no lumps. Stand 10 minutes. Heat cooking oil in a deep saucepan. Lightly dust mussels with a little flour, then tip them into the batter. Carefully drop into hot oil, one by one, and cook until the batter is golden (it may be best to cook them in several batches). Drain on kitchen paper. Serve with the sauce and a lemon wedge.