Place a large skillet in the oven and preheat to 325°F.
When the oven is hot add 1 teaspoon of the olive oil to the pan, swirl until well coated and add the mushrooms. Toss well and return the pan to the oven.
Roast the mushrooms for about 25 minutes until well browned. Toss frequently.
While the mushrooms are roasting place the water in a large pot over high heat and bring to a boil.
When the water is boiling add the pasta. Stir well and cook for 15 to 20 minutes. Do not cook until tender but until just shy of being al dente.
While the pasta is cooking place the remaining 3 teaspoons of olive oil in a large skillet over medium high heat.
Add the flour and cook for about one minute. This will be the consistency of coarse cornmeal.
Add the milk 1/2 cup at a time and whisk until the sauce begins to thicken.
Add the wine, chicken stock, thyme, salt and pepper.
Cook for about 3 minutes until the sauce begins to thicken.
Add the peas and chicken and toss well.
Add the cooked mushrooms and toss well.
Drain the pasta and add to the pan. Toss well.
Place the mixture in a 10 inch Pyrex baking dish.
Place the dish in the oven and bake for 40 minutes.
Top the casserole with the parmesan cheese and bake for another two minutes.
Let cool slightly before serving.
