Combine all the ingredients together in a small saucepan and bring it to a boil. Then, let it simmer until the sugar completely dissolves. Remove from heat and set aside to cool completely.
Udon Broth
Combine all the ingredients together in a saucepan and bring it to a boil.Then, lower the heat and let it simmer until the sugar completely dissolves. Remove from heat.
Heat up the broth again just before serving.
Tempura Coating
Combine the ingredients together in a wide dish.
Tempura Batter
Whisk in the cold water (cold makes the tempura crispier) into the frying mix until it has a smooth consistency. Add in the ice cubes.
Tempura
Prepare the tempura by slicing the vegetables.For the shrimp, make tiny scores on the bottom of the shrimp, and also on one of the sides. Make sure to not cut too deep. Gently pull it apart to make the shrimp straight. Repeat for the remaining shrimp.
In a medium-sized pot, heat up the neutral oil for frying until it reaches to 350ºF (180ºC).
Start off with the vegetables first. Coat the vegetables with the flour coating, and then dust off excess flour.Dip into the wet tempura batter.Deep fry for 2-3 minutes, until golden brown. Do not overcrowd the pot.Transfer to a wired rack or a plate lined with paper towel to drain excess oil.
For the shrimp: Coat the shrimp with the flour coating, and then dust off excess flour.Dip into the wet tempura batter.Grab the shrimp by the tail with chopsticks or heat proof tongs, and gently place into the heated oil, while making a swirling motion (this makes the shrimp straight).Deep fry for 2 minutes, until golden brown. Do not overcrowd the pot.Transfer to a wired rack or a plate lined with paper towel to drain excess oil.
Assembling the Tempura Udon
Place the cooked udon in separate bowls, and pour in the hot udon broth.Top with the tempura, and chopped green onion.