2 Heat and season the stock. Meanwhile, in a large saucepan over medium heat, bring the stock to a boil. Add the ginger, garlic, sesame oil and salt to taste. Adjust the heat to a gentle simmer, cover, and let it cook while you poach the eggs. This gives the flavors time to mingle.
Crack 1 egg into a small bowl or measuring cup. Hold the rim of the bowl or cup as close to the surface of the water as possible, and gently tip the egg into the water. Rapidly repeat with the remaining eggs.
Set a timer for 2 minutes to time the poaching. Stir the pot gently by dragging a wooden spoon around the edge of the pot, stirring the water just enough to cause the eggs to release from the bottom of the pot. You should see them bob a little in the water.
After 2 minutes, lift 1 egg from the water with a slotted spoon and test for doneness by pressing on the egg. The white should feel firm and the yolk should still be soft. Return to the water if necessary to complete the cooking.
With a slotted spoon, transfer the eggs to the paper towel lined plate. Place a lid on the pot to keep the water warm. (At this point, the eggs can be refrigerated, submerged in a container of water, for up to 5 days.)
Stir in the spinach. Stir gently until the spinach has wilted, about 30 seconds.
5 Assemble the bowls: Divide the noodles, broth, and spinach between 4 bowls.
4 Reheat the eggs, if necessary: If the eggs no longer feel warm to the touch, use a slotted spoon to gently drop them into the warm egg poaching water and leave for a few seconds to warm them. Remove with a slotted spoon. (If the eggs have been refrigerated, heat a pan of water to steaming before warming the eggs.)