Classic Tempura Soba Noodles (天ぷらそば)

Name: Classic Tempura Soba Noodles (天ぷらそば)
Prep time: 15 min
Cook time: 15 min
Total time: 30 min
Cuisine: Japanese
Ingredients: 200 ml cold water (chilled); 100 ml sparkling water (chilled); 30 g potato starch (sifted and chilled in fridge); 150 g cake flour (sifted and chilled in fridge); cake flour (for dusting); 1 medium egg (chilled); 8 giant tiger prawn (or similar large prawns); 4 fresh shiitake mushroom (stems removed); 100 g eggplant (cut into wedges and soaked in cold water); 8 perilla leaves (ooba/shiso); cooking oil (for deep frying); 1000 ml dashi stock; 5 tbsp soy sauce; 2 tbsp mirin; 1/2 tsp salt; 400 g dry soba noodles (approx 100g per serving); finely chopped green onion (to garnish); 12 slices Japanese fish cake "kamaboko" (optional, kamaboko); Japanese chili powder (shichimi togarashi, optional)