In a medium saucepan, combine the sugar, butter, milk, and cocoa powder
Bring to a boil, stirring occasionally
Once it reaches a rolling boil, let it boil for 1-2 minutes. Remove from heat
Stir in the peanut butter and vanilla extract until smooth
Put small spoonfuls of the mixture onto parchment paper on a plate
Allow to cool and set for about 30 minutes.