Melt the butter in a large saucepan over medium-high heat. Add the vegetables and cook until softened and well browned, about 9 minutes. Stir in the flour and cook, stirring constantly, until thoroughly browned about 5 minutes.
Gradually whisk in the broths and bring to a boil. Add the bay leaf, thyme and peppercorns and simmer, stirring occasionally, until thickened, 20 to 25 minutes, skimming off any foam that forms on the surface.
Pour the gravy through a fine-mesh strainer into a clean saucepan, pressing on the solids to extract as much liquid as possible. Discard the solids. Season the gravy with salt and pepper to taste.
Recipe by Culinary Mamas at https://culinarymamas.com/no-turkey-needed-gravy/