Roast the butternut squash. Heat your oven to 425°F (220°C fan). Slice the squash in half lengthwise and scoop out the seeds. Drizzle the exposed squash flesh with the olive oil and sprinkle with salt. Roast, cut-side down, on a parchment paper-lined baking sheet for 30 minutes, until soft and tender. You should be able to easily pierce the squash with a knife.
Cook the chorizo (optional). While the squash roasts, set a large, high-sided skillet or pot over medium heat, then add the diced chorizo. Cook, stirring, for a few minutes, until it releases oil and gets lovely and crispy. Remove the chorizo from the pan and set aside.
Build the broth. To the same pan, add a little drizzle of oil, then add the ginger, garlic, and ground turmeric. Cook, stirring, for a minute, then add 3 tablespoons of gochujang paste, 2 tablespoons of peanut butter, 2 tablespoons of light soy sauce, and 2 teaspoons of fish sauce. Stir for another few minutes, until it forms a thick paste.
Add coconut milk and stock. Pour in the coconut milk and 3 cups of chicken stock, then use a whisk to mix the paste into the liquid to form a lovely creamy broth. Stir, reduce the heat, and bring to a simmer.
Add the roasted squash. Scoop the roasted squash flesh out of its skin and add to the broth. Stir through, breaking the flesh up with your spoon and spatula. Return to a simmer for five minutes.
Blend the broth. For ease, use an immersion blender directly in the pot to blend the broth into a silky smooth soup. Or, for a slightly more velvety texture, transfer to a stand blender.
Cook the noodles and bok choi. I like to cook the noodles straight in the broth because I like the ramen more saucy than soupy - but if you prefer a soupier ramen, cook the noodles separately, drain, then divide between serving bowls. Use the packet instructions as your guide here. Halfway through the noodle cooking time, add the bok choi to the broth and stir through to gently cook.
Finish and serve. Taste, then add the lime juice and any extra seasoning if you think it needs it (I sometimes add a little extra fish sauce). Divide the noodles and broth between bowls, then add your desired toppings. Serve while hot and enjoy.