Adapted from BH&G Test Kitchen
Pour the drippings from your roasted turkey or chicken into a 2-cup liquid measuring cup. Skim off the fat, reserving 1/4 cup fat. If there are drippings stuck to the roasting pan, add the cider and brandy to roasting pan, stirring to loosen brown bits.
Add the cider mixture to the skimmed drippings. Add enough broth or stock to equal 2 cups.
In a medium saucepan, place the reserved fat. If there's not 1/4 cup fat, add butter to make up the difference. Whisk in the flour. Cook and stir over medium heat for about one minute.
Add the drippings mixture all at once. Cook and stir over medium until thickened and bubbly. Cook and stir one additional minute. Season with kosher salt and black pepper.
If desired, garnish with chopped fresh herbs before serving.
To make ahead: Prep as directed, using 1/4 cup butter in place of turkey fat. Combine the cider and brandy; add enough broth to equal 2 cups. Melt the butter in a saucepan and cook as directed in Step 2; cool slightly. Transfer to an airtight container; refrigerate up to 3 days.
When ready to serve, reheat the prepared gravy in a saucepan. If you like, add 2 to 3 tablespoons of drippings from your roasted turkey or chicken for extra flavor.