Melt butter in a sauce pan or skillet over medium heat.
Add flour to butter and whisk constantly until smooth, about one minute.
Slowly whisk in milk until well combined. Bring mixture to a low boil then lower the heat and simmer until thickened. Add more milk if thinner consistency is desired.
Stir in salt and pepper.
Serve warm.
Notes
Store leftover gravy in the refrigerator in airtight containers for three or four days.
If gravy is frozen, let it thaw in the refrigerator first.
Take cold gravy and spoon it into a cold skillet or sauce pan. Break it up with a spoon or a whisk.
Turn the heat to low and gently heat it thoroughly while stirring constantly. Serve warm.