Preheat oven to 350 degrees. Heat a grill pan to medium high heat. Pat the chicken breasts dry, season with salt and pepper, and grill for 3 to 4 minutes per side, or until no pink remains in the middle. Remove from heat and allow to cool. Meanwhile Heat the butter in a large saute pan over medium heat. Add garlic and saute one minute. Sprinkle in the flour, and whisk for a minute to cook out the raw flour taste. Slowly add the chicken stock and milk, whisking to combine until smooth. Bring the mixture to a simmer. Let cook for an additional minute until thickened, then whisk in 1/2 cup parmesan cheese. Season with salt, pepper, and nutmeg to taste. Add the sundried tomatoes, chicken, and zoodles to the sauce. Toss to combine well. Pour mixture into a 2 quart baking dish. Sprinkle with the parmesan cheese. Bake uncovered for 30 minutes.