Step 1: Heat sesame oil in a small pan over medium heat. Sauté sliced onion until softened, about 5-7 minutes. Add minced garlic and grated ginger, and cook for another 1-2 minutes until fragrant.
Step 2: Transfer the sautéed onion, garlic, and ginger mixture to your slow cooker. Add vegetable broth, soy sauce, rice vinegar, maple syrup, sliced mushrooms, cubed pressed tofu, and sliced carrots to the slow cooker.
Step 3: Stir everything gently to combine. Cover and cook on low for 4 hours, or on high for 2 hours, until the vegetables are tender and the flavors have melded.
Step 4: About 15-20 minutes before serving, add the white parts of the bok choy to the slow cooker. Cook the ramen noodles according to package directions in a separate pot of boiling water. Drain well.
Step 5: Turn off the slow cooker. In a small bowl, whisk the miso paste with 1/4 cup of the hot broth from the slow cooker until smooth. Pour the miso mixture back into the slow cooker and stir well to combine. Do not boil the broth after adding miso.
Step 6: Add the green leafy parts of the bok choy to the slow cooker and stir until just wilted by the residual heat.
Step 7: Divide the cooked ramen noodles among serving bowls. Ladle the hot vegan ramen broth with vegetables and tofu over the noodles.
Step 8: Garnish each bowl generously with chopped scallions, a drizzle of sriracha for heat (if desired), and a sprinkle of toasted sesame seeds and nori strips. Serve immediately and enjoy your comforting Slow Cooker Vegan Ramen!