Mince the garlic cloves and grate the ginger. Separate the whites from the greens of the green onions; chop the whites finely and slice the greens for garnish. If using bok choy, chop it roughly. If using soft-boiled eggs, prepare them according to your preference.

Heat a medium frying pan over medium-high heat. Add the sausage meat (casings removed) and break it apart with a spoon. Cook, stirring frequently, until browned and cooked through, about 5-7 minutes. Drain any excess fat. Stir in 1 tbsp soy sauce, 1 tsp sesame oil, and 1 tsp sriracha (if using). Cook for another minute, then remove from heat and set aside.

In a large pot, combine chicken or vegetable broth, the chopped white parts of the green onions, minced garlic, grated ginger, 1 tbsp soy sauce, 1 tbsp mirin, and 1 tsp chili garlic sauce. Bring to a simmer over medium heat. Once simmering, reduce heat to low. In a small bowl, whisk the miso paste with a ladleful of the hot broth until smooth, then stir the diluted miso back into the pot. Keep warm over low heat.

Add the ramen noodles (discarding flavor packets if using instant ramen) to the simmering broth. Cook according to package directions, typically 2-3 minutes for instant ramen or 4-5 minutes for fresh. During the last minute of cooking, add the chopped bok choy or spinach to wilt.

Divide the cooked noodles and greens evenly between two large ramen bowls. Ladle the hot miso broth over the noodles. Top each bowl generously with the spicy cooked sausage. Garnish with sliced green onion greens, soft-boiled eggs (if using), nori sheets (if using), and a sprinkle of toasted sesame seeds. Drizzle with extra chili oil for more heat, if desired. Serve immediately.