This chicken tetrazzini is comforting and supremely creamy; a cheesy pasta bake loaded with juicy chicken and plump mushrooms. It is widely believed to have been invented circa 1908–1910 by Ernest Arbogast, the chef at the Palace Hotel in San Francisco, California, where Tetrazzini made her American debut at the Tivoli as Gilda in Rigoletto on January 11, 1905
Preheat Oven to 350˚F. Cook pasta in a large pot of salted water until aldente according to package instructions then rinse to stop the cooking process, drain and set aside.
Cut 4 cups of chicken meat from a rotisserie chicken and shred into bite-sized pieces and set aside.
Place a large dutch oven or pot over medium/high heat. Add 2 Tbsp oil then add sliced mushrooms and sauté 3 min or until softened. Add diced onions and cook until onions are soft and golden, 5-7 min. Add minced garlic and sauté another 1-2 min until fragrant. Remove to the cutting board with chicken.
In the same pot, melt 4 Tbsp butter and whisk in 1/3 cup flour until lightly golden (1 1/2 min). Add 2 1/2 cups chicken broth, 1 Tbsp lemon juice, 1 tsp salt, 1/4 tsp pepper and whisk until smooth. Add 1 1/2 cups half and half and bring to a simmer. Season sauce with more salt and pepper to taste.
Return chicken, mushrooms, onions and pasta to the pot then sprinkle in 1/4 cup chopped fresh parsley and stir to combine. Sprinkle the top generously with shredded mozzarella, cover and bake at 350˚F for 30 min then remove lid and continue baking 15 min.**
To cook your own chicken: in your dutch oven or pot, melt 1 Tbsp butter and 1 Tbsp oil over medium-high heat. Season 2 lbs chicken breasts with about 1/2 tsp salt and 1/4 tsp pepper. Once oil is hot, saute chicken until golden brown on both sides and cooked through (about 4 min per side). Remove to cutting board to cool then cut into bite-sized pieces.**If baking in a 13x9 casserole dish, cover with foil and bake 25-30 minutes then bake uncovered an additional 10-15 min (it bakes 5-10 min faster in a casserole dish)