
Heat beef fat and oil over medium high heat in a small saucepan. Add flour and stir occasionally until mixture is golden brown and smells nutty.
Pour in 1/2 cup liquid and stir until smooth. Add remaining liquid and stir until combined.
Bring to a boil, stirring constantly. Reduce heat and simmer 2 minutes.
Season to taste with salt and pepper.
Stir in 1 Tablespoon of butter if desired for a silky sheen.
Serve immediately.