Beat butter, brown sugar and granulated sugar together until fluffy. About 3 minutes. Beat in eggs one at a time. Scraping down the sides of the bowl after each egg. Beat in vanilla extract.
In another bowl combine flour, baking soda and salt. Slowly beat flour mixture into egg mixture. Mix well. Fold in semi-sweet chocolate chips and peanut butter cups.
Roll out tablespoonfuls of dough and place them on cookie sheets. Bake for 10 minutes or until edges have started to brown.
Note: when baked for 10 minutes these are chewy cookies. Baked for 12 minutes they get a bit crispy.
Allow to cool on the baking sheet for a few minutes. Transfer to a cooling rack to cool completely.