In a small saucepan, heat the oil, crushed red pepper and garlic over medium-high heat until the garlic sizzles. Lower the heat to low and cook, stirring, until the garlic turns golden, about 3 minutes. Turn off the heat and let the mixture sit for at least 30 minutes. Strain the chile oil into a bowl, discarding the solids.
Meanwhile, bring a medium pot of water to a boil. In another medium pot, mix the chicken broth, mushrooms, scallions, soy sauce, sugar and ginger. Cover and simmer over high heat for 8 minutes. Lower the heat, cover and simmer until the mushrooms are soft, about 5 minutes. Turn off the heat; discard the ginger. Stir in the spinach, then the tofu. Cover to keep warm.
Add the ramen to the boiling water, breaking up the noodles. Cook until tender, 3 minutes. Drain, then stir the noodles into the soup. Season with salt.
Divide the soup among bowls. Drizzle each with some of the chili oil.