Preheat oven to 400°.
In a double boiler over medium heat add the chocolate broken into pieces and the butter. Stir until melted and remove from heat to cool slightly.
In a medium bowl, combine the eggs and sugar and beat until light and fluffy.
Add the cooled chocolate and vanilla.
Mix in the flour and a dash of salt.
Gently stir in chopped peanut butter cups.
Scrape the batter into a 9" x 13" baking dish that has been buttered.
Bake at 400° for 30-35 minutes or until a wooden pick inserted into the center of the pan comes out clean.
Cool completely and cut into squares.
