Drizzle 2 tbsp of vegetable oil into a large pan, and turn the heat on.
Toss in the onions, and cook until they are translucent.
Next add in the garlic, and stir.
Remove ingredients from the pan.
Toss the butter into the pan.
Once the butter is melted, sprinkle in the all purpose flour.
Cook until the flour is lightly browned.
Slowly pour in the chicken broth, and half & half, then whisk.
Reduce the heat to low medium, and let simmer for 5 minutes.
While the sauce is simmering cook the linguini.
Combine the sauce, chicken, mushrooms, onions, garlic, lemon juice, lemon zest, and fresh basil.
Combine all the cheeses in a bowl.
Toss half of the cheese mixture into the bowl with the chicken, and etc.
Next, add in the pasta, and fold the ingredients.
Preheat the oven to 350 F.
Lightly oil a large casserole dish, and add in the pasta.
Top with the remaining cheese.
Bake, uncovered, for 35 minutes.
Serve and enjoy!