Line a cookie sheet with parchment paper; set aside.
Put the cereal in a resealable plastic bag and crush by running a rolling pin over the cereal a couple of times.
In a large bowl or stand mixer, mix together the SunButter, the crushed cereal and softened butter.
Gradually add the powdered sugar, mixing until a thick dough forms. You may need to adjust the amount of powdered sugar slightly to achieve the right consistency. If the dough is crumbly or too thick, add a tablespoon of milk or melted butter until desired consistency is reached.
Once the dough is firm enough to handle, use a cookie scoop and shape it into small 1-inch balls. Roll the scooped balls in your hands to make smooth, if needed.
Place the rolled balls onto the cookie sheet that is lined with parchment paper or a silicone baking mat.
Refrigerate or freeze for about 20 minutes or until firm.
In the meantime, melt the chocolate in a microwave-safe bowl in 30-second intervals. Stir the chocolate after each interval, until smooth and melted.
Remove the balls from the refrigerator or freezer. Using dipping tools, a fork or toothpick, dip each ball about three-quarters of the way into the melted chocolate, carefully shaking off the excess chocolate. The top portion typically remains uncovered for the classic buckeye look.
Place the dipped buckeyes back on the cookie sheet. Let the chocolate harden completely at room temperature or refrigerate for a faster set. When set, the chocolate coating should firm.
Once the chocolate is fully set, carefully remove any toothpicks or skewers that you may have used when dipping.
Store in a food-safe container in the refrigerator. Put parchment paper in between each layer of buckeyes.