Preheat oven to 400 degrees F and prepare two medium sized baking dishes. Cook pasta until al dente, or slightly undercooked. Reserve 3 tbsp of pasta water before draining pasta and setting aside.
In a skillet, add olive oil and heat until warm. Season chicken with salt, pepper, and any additional spices, before cooking over medium heat.
In another pot, melt butter over medium heat. Add the flour and garlic, cooking for one minute. While mixing, slowly add the milk and bring the mixture to a simmer, until it's thickened. Add chicken, sundried tomatoes and mushrooms. Turning the heat off, add the mozzarella cheese and mix well.
Pour the chicken mixture slowly over the pasta, mixing well. Divide the pasta mixture into the two baking dishes. Bake one for 25 minutes or until the top is golden, and cover and freeze the other for up to 3 months, baking it for 1.5 hours.