On a baking sheet of about 9x13 inches in size, place a piece of parchment paper.

In a large bowl, melt the chocolate chips in the microwave in short 30-45 second bursts stirring after each. Or melt on the stove top using a double boiler. Pour the melted chocolate onto the prepared baking sheet and using a flat edge icing tool to spread the chocolate smooth. It won't take up the entire baking sheet - just spread to be about ¼ inch thick.

In a separate small bowl, melt the peanut butter chips with the oil in the microwave in short 30-45 second bursts stirring after each. Or melt on the stove top using a double boiler. Spoon into a small piping bag or into a ziplock bag and cut off the bottom edge. Pipe the melted peanut butter chips onto the first chocolate layer. Then scatter Reese's Pieces and pretzels over top.

Allow to harden at room temperature. Then break or cut into pieces.