Melt butter, sugar and evaporated milk, stirring for 5 minutes. Add vanilla and salt under the fudge has reached 235 Degrees on a Candy Thermometer, or balls up when dropped in a glass of cold water.
Pour mixture into 8 x 8 inch pan and allow it to cool before placing in the fridge for an hour.
Cut desired sized squares and serve. Can be stored in the fridge for up to 5 days.