Peanut Butter Cups

This is my aunt Vivian's recipe:

6 whole Graham Crackers, crushed
1 cup Peanut Butter
1 1/2 cups Powdered Sugar
1/2 cups Melted Butter
1 package Chocolate Chips

Mix ingredients together. Spread on cookie sheet and chill. Take chips and melt over low heat or using a double boiler. Spread over peanut butter mix. Cool and cut into squares.