In a microwave safe bowl, add sweetened condensed milk and chocolate.
Place in microwave and heat for 3-minutes, stirring every 30-45 seconds until chocolate is melted
Remove from microwave, stir in vanilla.
Line an 8"x8" pan with parchment paper.
Pour mixture into pan. Top with nuts if desired.
Cover and refrigerate for 2 hours or until set and completely cooled through.
Cut into 1" squares and serve.
Store in an airtight container.