Preheat the oven broiler to high and line a baking sheet with foil.

Make the broth: Place the onion wedges and ginger, cut side up, on the baking sheet. Broil for 10 to 20 minutes, or until charred. If the ginger is ready before the onions, remove it from the baking sheet and continue broiling the onion until soft and well charred around the edges.

Heat a large pot or Dutch oven over medium heat. Add the star anise, cloves, cinnamon sticks, coriander, and fennel seeds and cook, stirring, for 3 minutes, or until fragrant. Add the water, onions, ginger, mushroom stems, kombu, and tamari. Simmer for 30 minutes.

Place a fine mesh strainer over a large heatproof bowl and strain the broth into the bowl. Discard the spices, onions, ginger, mushroom stems, and kombu.

Meanwhile, make the soup: Heat the avocado oil in a large skillet over high heat. Add the mushrooms and a pinch of salt and cook, stirring only occasionally, for 4 minutes, or until the mushrooms are browned and starting to soften.

Nestle the bok choy wedges into the skillet so that the cut sides make contact with the pan. Cook for 1 minute, then add the rice vinegar and cover. Reduce the heat to medium and cook, stirring occasionally, for 5 to 7 minutes, or until the bok choy is tender. If the pan becomes dry, add 2 tablespoons water. Remove from the heat and set aside.

Prepare the noodles according to the package instructions, then divide among four large soup bowls. Add the mushrooms, bok choy, and baked tofu. Ladle in broth to cover.

Top each bowl with bean sprouts, if using, jalapeños, basil, and cilantro. Serve with lime wedges for squeezing, sriracha, and more tamari.