Bring a large pot of water to a boil for the pasta. Once boiling, add the paccheri and cook for 4 to 5 minutes (be careful not to overcook).

Meanwhile, heat a drizzle of olive oil in a small skillet and add the mushrooms (drained, if using canned or jarred). Sauté over low heat for about 10 minutes, then season with a pinch of salt and some chopped parsley.

In another skillet, heat a drizzle of olive oil and crumble in the sausages. Slice half an onion and add it to the sausages. Sauté until the sausage is cooked through. Then add the mushrooms to the sausage and mix well with a wooden spoon. Finally, add the béchamel sauce and stir until everything is well combined. Preheat the oven to 400°F (200°C).

Drizzle a little olive oil in a baking dish and add 3 tablespoons of the sausage, mushroom, and béchamel mixture. Arrange the paccheri side by side in the dish and cover with more of the mixture. Continue layering until the dish is full and all ingredients are used. Bake for 5 to 10 minutes.