Heat canola oil over medium heat. Add sliced mushrooms to canola oil. Continue cooking, stirring frequently, until soft and lightly browned. Note: Don’t add salt to this process.
Add both the vegetable broth and miso paste to the mushrooms, and bring to a boil over medium-high heat. Once boiling, add cabbage and the soba noodles. Cook as per time advised on the soba noodle package.
Once noodles are cooked, remove from heat. Garnish with scallions. Serve immediately.