In a large saucepan on low-medium heat, melt the white chocolate and shortening.

Whisk vigorously until very smooth.

In a greased 7x11-inch baking dish or pan, spread slightly more than half the white chocolate evenly into the bottom. It needs a sturdy base. Allow to set.

Meanwhile, in a large mixing bowl, combine peanut butter, butter, vanilla, and powdered sugar until well-combined. Add enough powdered sugar that it's very thick and not-greasy, but not so that it's crumbly. It needs to adhere to the chocolate!

Using your hands, press the peanut butter mixture over the white chocolate in an even layer.

Spread remaining white chocolate on top of peanut butter layer.

Sprinkle mini Reese's pieces evenly over white chocolate, and press them lightly into the chocolate. The little devils want to pop off, so press them in a bit.

Allow to set.

Store in the refrigerator. Cut into bars. Enjoy!