In a Dutch oven or stockpot, heat the olive oil over medium-high heat. Add the pork and cook until brown, using a wooden spoon to break it up. Use a slotted spoon to transfer the pork to a paper towel-lined plate. Add the sweet potatoes and saute until beginning to become tender, 7 to 8 minutes. Add the mushrooms, ginger and garlic and cook until the mushrooms release their water and begin to brown, 5 to 7 minutes. Season with salt and pepper.
Add the chicken broth, using a wooden spoon to scrape up any browned bits on the bottom of the pot. Add the soy sauce, mirin, sesame oil, brown sugar, celery seed and browned pork. Bring to a boil, reduce the heat to a simmer, cover and let simmer 15 minutes. Add the ramen noodles. Simmer until tender, about 5 minutes.
Serve in a bowl with an egg on top. Garnish with Sriracha and cilantro.