Put 7 cups (1680 ml) of water in a large pot and bring to a boil.
Remove from the heat and let it cool for 2 minutes to avoid scorching the tea.
Stir in the green tea leaves, cover, and steep for 5-10 minutes until fragrant and richly colored.
Strain the tea broth into a large saucepan, discarding the tea leaves.
Bring the broth to a rolling boil.
Add a generous pinch of salt and stir in the udon noodles.
When the broth returns to a boil, add 2 cups (480 ml) of cold water. This classic technique prevents the noodles from overcooking on the outside while the inside cooks through.
When the liquid returns to a gentle boil, reduce the heat to a simmer.
Cook, stirring occasionally, for 5-7 minutes or until the noodles are just tender.
Taste the broth and season with more salt, a few grinds of black pepper, and the optional mirin or sugar for a touch of sweetness.
Serve immediately.
Add plant-based protein by stirring in 1/2 cup (480 ml) of cubed firm tofu or 1 cup (240 ml) of cooked edamame during the last few minutes of cooking.
Turn up the heat by adding a pinch of cayenne pepper or a dab of wasabi paste to each bowl.
