Preheat oven to 375 degrees F (190 degrees C). Line a half sheet pan with parchment paper or foil and arrange crackers on top. May need to break crackers to fill in gaps. Set aside.
In a medium saucepan stir together the butter and brown sugar over medium heat. When it starts to boil stop stirring and let boil for 3 minutes. Pour over crackers in an even layer then bake for 6 minutes.
Meanwhile, melt peanut butter in a small bowl until smooth and pourable. Remove toffee from oven and drizzle with the peanut butter. Sprinkle with chocolate chips then return to the oven for 1-2 minutes to help soften the chocolate chips. Remove from oven and spread out chocolate and peanut butter as much as you like. Top with chopped peanut butter cups.
Let sit for 2 hours or until chocolate is set. I like to refrigerate this to speed things up. Once set, break into pieces. Store in an airtight container for up to 2 weeks.
1. This can also be frozen for up to 2 months.