Bring a medium-large pot of salted water to a boil. Once boiling, add the pasta and cook for approximately 10 minutes. Before straining, reserve β cup of pasta water for later use. Strain the pasta and set it aside.
Give your vegetables a quick wash where needed, and cut them as shown below.
Heat a large pan over medium-high heat with a splash of oil. Once hot, add the sliced mushrooms and cook for 6 minutes, until they begin to brown around the edges. Add the broccoli and green pepper, and cook for another 6 minutes, stirring occasionally.
Add the dan dan sauce, reserved β cup of pasta water (or ΒΌ cup regular water if you forgot to save it), and the cooked fusilli pasta to the pan. Cook for 6-7 minutes, stirring occasionally, until the sauce thickens and clings to the noodles.
To serve, place the pasta in a bowl or on a plate and garnish with green onion and sesame seeds.