Heat the coconut oil in a stockpot over medium heat.
Add the minced garlic, diced jalapeño, minced ginger, and diced scallions; cook until fragrant and softened, about 3 to 4 minutes.
Transfer the cooked aromatics to a blender and add the green curry paste, lime juice, cane sugar, coconut milk, and 1/3 cup cilantro; puree until smooth to make the curry sauce.
In the same or a clean pot, combine the vegetable broth and water and bring to a boil.
Reduce to a simmer and add the udon noodles; cook until just tender according to package timing.
Stir the pureed curry sauce into the pot with the cooked noodles, then add the baby spinach and cook about 1 minute more, until the spinach wilts.
Taste and season with salt as needed.
Divide the noodles and broth between two bowls and top each with a poached egg, toasted coconut flakes, reserved scallion greens, and extra cilantro if desired.