This is the recipe that my mom uses when she make homemade gravy (to her there is no other kind of gravy) There was no changing to the recipe since she only uses cornstarch for her gravy.
Add 1 cup stock to bottom of roasting pan; carefully scrape browned bits from bottom of pan. Add remaining 1 1/2 cups stock to pan; bring to a boil over medium-high heat. Combine 6 tablespoons no fat half and half and 2 Tlb. of cornstarch, stirring with a whisk until smooth. Stir cream mixture into stock mixture, stirring with a whisk. Boil 1 minute or until slightly thick, stirring constantly. Serve gravy with the turkey.