Line the bottom of a 9x13 inch pan with parchment paper or silicone baking sheet. Set aside.
Melt half of the chocolate according to package directions and pour into lined pan. Spread the chocolate into an even thin layer and set aside to firm up (can be placed in the refrigerator or freezer if desired).
In the bowl of a stand mixer fitted with the paddle attachment, beat together the peanut butter, powdered sugar, butter and vanilla until smooth. Set aside 1/4 - 1/2 cup of the peanut butter mixture.
Press the rest into an even layer onto the chocolate layer. Use hands as necessary to flatten. Use remaining 1/4 - 1/2 cup peanut butter mixture to roll into small buckeye balls about the size of a dime.
Melt the remaining chocolate and pour it over the peanut butter layer. Drop the mini buckeye peanut butter balls all over the pan. Set aside to become firm.
Once chocolate is set, use a large knife to break up the bark into pieces. Store in the refrigerator.