Cut spinach leaves into 1/2-inch strips; set aside. Heat a saucepan over medium heat. Add onion, carrots, and celery. Cook, stirring occasionally, until vegetables are golden and tender, about 10 minutes.
Add wine, and cook until evaporated, about 3 minutes, stirring with a wooden spoon to loosen any browned bits on the bottom of the pan.
Add stock, 2 cups water, peppercorns, and bay leaves, and bring to a boil. Reduce to a gentle simmer, and cook 30 minutes to allow flavors to infuse.
Strain stock through a fine mesh strainer, discarding solids. Return strained stock to clean saucepan, and bring to a simmer. Add the beaten eggs, stirring gently so they form long threads. Stir in spinach, and cook until just wilted, about 1 minute. Season with salt and pepper, and serve immediately.