Toss pot roast cubes with salt and pepper. Heat a large skillet oven over medium- high heat, spray with oil and brown the beef on all sides about 4 minutes total. Transfer the beef to the slow cooker, then spray the skillet again.
Add the mushrooms to the same skillet and brown, 2 to 3 minutes, stirring halfway. Add the ginger, garlic and scallion; cook until aromatic, about 1 minute. Transfer mushrooms and aromatics to the slow cooker.
Add beef broth and soy sauce to the slow cooker; cover and cook on high for 6 hours.
In the last 10 minutes of cooking, add ramen noodles* and baby bok choy and cook until tender.
Serve bowls of ramen with halves of soft boiled eggs and top with scallions and sesame seeds and a drizzle of sesame oil, if desired and optional toppings.
