Preheat the oven to 400 degrees F. Line a baking sheet with parchment paper.
Cut off the stem, slice the spaghetti squash in half, and scoop out the seeds. Drizzle the cut sides with a small amount of olive oil, season with salt and pepper, and place cut side down on the lined baking sheet. Bake for 25 to 30 minutes or until squash is tender but still crunchy and can be pulled with a fork. I personally like to slightly undercook the spaghetti squash and check it right at 25 minutes, so that the noodles don't get soggy in the broth later when you are serving the ramen. If you want to cook the squash for longer, feel free.
Prepare the eggs by placing them in a pot with enough water to cover them by 1 inch. Bring to a boil and cook for 8 to 10 minutes. A shorter cooking time will result in a softer boiled egg, if desired. Transfer the eggs to a bowl of cold water after cooking. To make perfect soft-boiled eggs that have jammy yolks (like you would get with restaurant ramen), consider using an electric egg maker.
While the squash is roasting, heat sesame oil in a large pot over medium heat. Add the onion, garlic, and ginger, and cook for approximately 5 to 7 minutes. Pour the vegetable broth into the pot, add the dried mushrooms, and bring to a boil. Reduce heat and simmer for at least 20 minutes (a longer simmer time will yield more flavor). Blend the broth in the pot using an immersion blender, or transfer it in batches to an upright blender. Strain the broth through a mesh sieve into a large bowl. Use a spoon to push down the mushroom puree in the sieve to extract as much liquid as possible. Alternatively, you can skip the blending step and strain the broth with the mushrooms and onions intact, but I think the broth is more flavorful if the mushrooms are blended into the liquid.
Return the strained broth to the pot, and thin with a cup of water if needed. Stir in the soy sauce, miso paste, and rice vinegar. Bring the broth back to a gentle simmer over medium-low heat, then place the bok choy in the pot. Cook for 3 to 4 minutes until the bok choy turns bright green and is steamed to your desired texture. Remove the bok choy and divide between two serving bowls. Taste the broth, and adjust the seasonings as desired.
Prepare 2 ramen bowls by placing 1-1.5 cups of spaghetti squash and 2 bok choy halves into each bowl. Divide the broth equally between each serving. Peel the boiled eggs and slice in half, then place in the bowls. Top with sliced scallions, toasted sesame seeds, and hot sauce to taste.