Combine first three ingredients in mixer on medium speed, then add in 1 cup of the peanut butter.
Spread evenly over the bottom of an ungreased 9x13 pan.
In small bowl, melt together chocolate and remaining 1/4 cup peanut butter in microwave fpr 30 seconds.
Stir peanut butter and chocolate chips. If chips do not melt, cook in microwave an additional 10 seconds at a time until melted.
Pour over the peanut butter mixture.
Refrigerate at least 3 hours, or overnight.