Steam broccoli florets for 4 to 5 minutes or until the stems are bright and green. Boil water and cook the soba noodles according to package directions.
Meanwhile, melt 1 tablespoon of butter and sesame oil together in a large sauté pan over medium high heat.
Add the mushrooms and cook without stirring for 2-3 minutes, watching so the mushrooms don’t stick to the pan or burn. Stir and reduce to the heat to medium then add the broccoli and the ponzu and miso tamari and cook together for 2-3 more minutes. Add the remaining tablespoon of butter, stir and season with ground black pepper. Garnish with lemon zest and sesame seeds and add more ponzu to taste.
Fill bowls with portions of soba noodles and top with the broccoli and mushrooms. Or, mix the noodles into the pan with the broccoli and mushrooms, stir, and serve together.