Mix the softened butter and peanut butter until blended and smooth. You can do this in a food processor, or with a hand held or stand mixer. Add powdered sugar, mix until the peanut butter mixture is dry enough to roll into balls without sticking. If using a stand mixer or food processor, pulse or turn off and on quickly a few times and then mix on low just until blended.
Roll into balls about 1" in diameter. Place on a cookie sheet in single layer, when the cookie sheet is full, place in the freezer or refrigerator until thoroughly chilled.
Place the chocolate in a glass bowl in the microwave or on the stove in a double boiler. Be careful not to burn the chocolate. In the microwave, melt at 30 second intervals. Remove and stir. Heat just until chocolate is melted.
After they chocolate is set, remove and store in Tupperware, Ziplocks bags or other covered container. These keep well for a long time in the refrigerator or freezer.