Preheat oven to 350*F. In saucepan, melt 2 TBSP butter. Add the flour and stir to thicken. Add the chicken broth, salt, pepper and sherry. Bring to boil, then stir continuously 3-5 minutes until a nice sauce forms. Add the cream, stir another 3-5 minutes.
Add chicken to the mixture, stir til warm and coated.
Butter a 9x13 pan. Pour linquine into bottom of pan to cover it. Pour your chicken/sauce mixture over the top - spreading to cover the pasta. Dot the top with the rest of butter. Sprinkle parmesan on top. Put slices of American cheese on top. Bake, uncovered, 30-45 minutes, until top is browned and bubbling.