Bring water to boil in a pot or wok. Add a teaspoon of salt and drizzle some cooking oil into the pot. Blanch the sweet potato shoots until they turn dark green in color. Remove from heat, drain and run shoots through some cold water very quickly to stop the cooking process. Heat oil in wok. Fry the garlic until golden brown. Remove fried garlic and set aside. Add sweet potato shoots to wok and stir briskly for 30 seconds. Add 2 tablespoons of hot water, and once water boils, turn off the heat. Add miso paste and stir well. Dish up and garnish with fried garlic slices.