Cheesy Chicken Tortellini Bake

½ c. finely chopped onion
1 clove garlic, pressed
1 t. olive oil
1 jar (16 oz.) white Alfredo pasta sauce
1 pkg. (20 oz.) refrigerated cheese-filled or spinach tortellini
1½ c. cooked chicken
1 c. milk
1 c. water
1 t. dried basil leaves
Optional: 1 c. frozen peas, grated Parmesan cheese

In Executive 4-qt. Casserole, heat oil and cook onion and garlic until tender. Stir in remaining ingredients; cover with lid and bake at 400°F for 25 min. Cool completely and pour into freezer bag. Squeeze air out of bag and freeze. Defrost in refrigerator for 24 hours. Bake, covered, at 375°F for 25 min. May top with grated Parmesan cheese. (I found and used frozen tortellini but no refrigerated.)