Cook the pasta in boiling water for 15 minutes or until tender. Drain and set aside.

While the pasta is cooking, grill the asparagus and poblano pepper over medium-high heat for 6 minutes. Once the asparagus is cooked, set it aside. Clean the poblano pepper by removing the seeds and skin, then dice it.

Preheat the oven to 350°F (175°C). Grease a 12×8-inch baking dish. In a large skillet, melt the butter and cook the mushrooms. Add the diced poblano pepper.

Add the flour and stir until well combined. Gradually add the milk and about 1/4 cup water, cooking over medium heat until it starts to boil, stirring constantly. Add the cheese and stir until melted. Remove from heat and add the tuna and pasta to the mushroom mixture.

Combine all the ingredients together.

Transfer everything to the prepared 12×8-inch baking dish.

Arrange the asparagus on top and sprinkle with breadcrumbs mixed with the melted butter. Bake at 350°F (175°C) for 20 to 25 minutes.