Step 1: Rehydrate the shiitake mushrooms. Place dried shiitake mushrooms in a bowl and cover with 1 cup of hot water. Let them soak for 15-20 minutes until softened. Remove mushrooms, reserving the soaking liquid. Slice the rehydrated mushrooms if large.
Step 2: Combine broth ingredients in the slow cooker. Add vegetable broth, reserved mushroom liquid, soy sauce, rice vinegar, sesame oil, grated ginger, minced garlic, sliced rehydrated shiitake mushrooms, sliced carrots, and sliced red bell pepper to your slow cooker.
Step 3: Slow cook the broth. Cover the slow cooker and cook on high for 3-4 hours or on low for 6-8 hours, until the vegetables are tender and the flavors have melded beautifully.
Step 4: Prepare remaining ingredients. About 30 minutes before serving, cook the ramen noodles according to package directions in a separate pot until al dente. Drain well.
Step 5: Finish the ramen broth. Remove the lid from the slow cooker. Add the pressed and cubed tofu and fresh spinach. Stir in the white miso paste until it is fully dissolved. Do not boil the broth after adding miso to preserve its beneficial properties.
Step 6: Assemble the bowls. Divide the cooked ramen noodles among four serving bowls. Ladle the hot, flavorful Slow Cooker Vegan Ramen broth with vegetables and tofu over the noodles.
Step 7: Garnish and serve. Garnish each bowl generously with sliced green onions, a sprinkle of sesame seeds, a drizzle of chili oil (if desired), and a few strips of nori. Serve immediately and enjoy your comforting Slow Cooker Vegan Ramen!