How to Make It
Preheat oven to 425°F. Heat oil in a large skillet. Add mushrooms; cook, stirring occasionally, until mushrooms begin to wilt, about 4 minutes. Stir in nori and bamboo; cook, undisturbed, 1 minute.
Whisk flour and 1/2 cup of the stock in a small bowl until smooth. Add remaining 3 1/2 cups stock to mushroom mixture in skillet; bring to a boil over medium-high. Add flour mixture, soy sauce, and salt. Let mixture come to a simmer; simmer, stirring often, 1 minute. Remove from heat; stir in pork.
Arrange ramen noodles in an 11- x 7-inch casserole dish. Pour pork mixture over the top. Bake in preheated oven until bubbly, about 15 minutes.
Arrange eggs over casserole; sprinkle with scallions and togarashi.