Combine the dry mustard, vinegar, sugar and egg in the top of a double boiler and mix until smooth using a wooden spoon. Place over the heat and cook for four or five minutes until slightly thickened stirring with a wooden spoon. Chill
Remove from the heat and stir in the miso. Season to taste with salt and pepper
In a suitable bowl, combine the flour, baking powder and mint and mix well. Stir in the water and mix until smooth. Season to taste with salt and pepper
In a deep frier or deep pot, heat the oil to 350 F
Dip the beans into the batter and coat evenly. Remove from the batter and allow it to drip off slightly. Deep fry until golden brown
Remove the fried beans to a baking pan covered with absorbent towels and sprinkle with salt and pepper. Serve with the sauce on the side for dipping.
