Heat the bacon grease in a saucepan on medium-low heat.
When the bacon grease is hot, whisk in the flour one tablespoon at a time to prevent lumps from forming, stirring constantly. Cook the flour mixture for about 1 to 2 minutes.
Slowly pour the milk into the flour mixture, quickly whisking to combine until smooth.
Stir in the salt and pepper. Heat the mixture over medium heat, stirring constantly until the gravy thickens to your desired consistency. It will take about 5 minutes for the gravy to come to a low simmer and thicken.
Once the gravy is thick, remove from the heat. Add more salt or pepper to taste.
