Place the buckwheat and plain flours, grappa and salt to taste in a bowl. Gradually whisk in enough beer to form a smooth, thick batter; you may not need it all. Cover with plastic film and refrigerate for 1 hour.
Heat oil for deep-frying in a heavy-based saucepan or deep-fryer until it registers 180°C on a sugar/deep-fry thermometer. Working in b