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.
Notes
*Mixed mushrooms work great for their umami qualities; try using mushrooms like shiitake, maitake or shimeji. If using fresh ramen noodles, cook separately and pour soup over them in a bowl. Gluten-Free: Use rice ramen noodles for a gluten-free option.To Meal Prep or Freeze: Prepare the soup without the noodles and freeze or refrigerate, otherwise they will soak up the broth and get mushy. When heating up later, cook the noodles as directed and add to the soup.Additional ramen toppings: Top with chopped kimchi, sweet corn, bamboo shoots, bean sprouts, seaweed snacks, sriracha, sliced jalapeños, or shredded carrots.Makes 12 cups.