In a large saucepan set over medium heat, melt the butter. Add the garlic, sage, rosemary and thyme and cook, stirring until the garlic is softened and fragrant.
Add the cassava flour and continue to cook, stirring, until the flour is well combined with the butter, about 2 minutes.
Add the white wine and whisk to combine until the mixture thickens.
Slowly pour in 1 cup of broth, whisking constantly, until smooth. Pour in the remaining 3 cups of broth and continue to whisk until evenly combined.
Increase the heat and bring the gravy to a rapid simmer. Once simmering, continue to cook, whisking often until the gravy thickens, about 5 minutes. Remove from heat, cover, and keep warm until ready to serve. Season to taste with salt, as desired.