Cook the sugar and milk in a pot over medium heat.

Stir the mixture constantly to prevent burning. Use a candy thermometer.

When the mixture gets to soft ball stage, 238 degrees, remove from heat.

Add the peanut butter and stir well.

Add vanilla, be careful the vanilla will boil

Stir in the marshmallow

put the fudge mixture in a well buttered pan or parchment paper, make sure parchment paper is well buttered.

When fudge is completely cooled cut and serve.

Or you can take the cut pieces and cover with melted chocolate.