Remove the turkey from the roasting pan (or slow cooker for a turkey breast), pour the contents through the fine mesh sieve over a bowl, so that the drippings end up in the bowl. Discard the solids.

In a small bowl, place the 1 cup cold broth Sprinkle the gelatin powder over the broth. Set aside to dissolve.

Place the Turkey drippings and rest of the broth in a saucepan over high heat. Bring to a boil, then lower the heat to a simmer for about 20 minutes, until the gravy has reduced by half.

Add the dissolved gelatin mixture into the pan, whisking often, until dissolved.

Allow the gravy to cool from hot to lukewarm - it will thicken as it cools. It may form a film on top, but just whisk it and it will go away. It will gel and be too thick if it gets completely cold - just reheat it to make it pourable again.