If starting with pan drippings, remove any meat and vegetables from your baking pan. Scrape up all the browned bits on the bottom and sides. Strain drippings into a measuring cup.
Add stock until you have 2 cups of liquid. Pour into a saucepan and bring to a simmer.
Make a slurry from the starch and water. Mix thorough to make sure there are no lumps and nothing stuck on the bottom.
Once your liquid is a simmer, stir your slurry again. Slowly add to your pot while stirring your liquid. Continue stirring until your gravy is thickened and glossy.
Season with salt and pepper to taste.
Cornstarch is more translucent than flour based sauces. Potato starch gravy is more opaque than cornstarch but less opaque than flour.
Starch sauces require less simmering than flour based sauces. Do not boil. Don’t overcook cornstarch based sauces or your gravy will lose some of its thickness.
Starch based gravy can be made ahead and gently reheated, but may loose some of it’s thickness.
Starch based sauces do not freeze well.