Preheat oven to 350, butter a large deep baking dish 8 x 12 inches.
In a large pot of boiling salted water, cook pasta for about 6-7 minutes. You basically want to take it off before it has cooked throughout. Drain, rinse and set aside.
Put the chicken between two sheets of baking paper and hammer it out with a meat tenderizer. Careful no to tear up the chicken. You are just looking to flatten it to about 1 inch thick. Season chicken with salt and pepper and toss in a little of the garlic.
In a large non-stick skillet, heat one tablespoon of the oil over medium-high heat. Cook the chicken for about 2 minutes per side and remove from pan. You are not looking to cook the chicken throughout at this point. Slice up the chicken and set aside.
In the reserved pan from the chicken add the remaining tablespoon of olive oil and toss in the mushrooms and cook for 5 to 8 minutes. They should be browned and softened.
In a large heavy saucepan, melt butter over medium heat. Add flour and remaining garlic, cook, whisking constantly, about 1 minute. You will have a thick paste. While whisking, gradually add milk, bring to a simmer, whisking frequently. Gradually stir in the Gouda and about 2/3 of the parmesan. You should have quite a thick cheese sauce now. Toss in the herbs, the sun-dried tomatoes, salt and pepper. Give a good stir and set aside
Add the pasta, chicken and mushrooms to the baking dish. Pour over sauce and mix it together. Sprinkle over remaining parmesan cheese. Bake for about 20-25 minutes. Let it stand for about 5 minutes before serving.