In a large bowl, mix melted butter, peanut butter, crisped rice cereal, sugar and karo syrup. Line cookie sheets with wax paper. Scoop and roll into 1-inch balls and refrigerate for at least 4 hours. Melt chocolate in double boiler, adding 1/2 teaspoon of vegetable oil at a time, until dipping consistency. Dip balls in melted chocolate and place back on wax paper lined cookie sheet and refrigerate until chocolate is set.
Optional: sprinkle tops of candy with crushed peanuts after dipping in chocolate and before refrigerating.