Heat oil over high heat in a large skillet. Brown chicken. Reduce heat, and add garlic and mushrooms. Cook until soft. Remove chicken and mushrooms from the skillet.
Pour half and half cream into skillet, and bring to a boil over high heat. Reduce heat to medium, and reduce. Stir occasionally.
Meanwhile, cook the pasta in a large pot of boiling water until done. Drain.
When cream has reduced and thickened, stir in Gorgonzola until melted. Add chicken and mushrooms, pasta, and walnuts. Toss and reheat. Season with salt and pepper. Serve immediately. Garnish with freshly grated Parmesan cheese, if desired.