In the bowl for a stand mixer, cream together the butter and sugars.
Add the egg, peanut butter, salt and vanilla. Mix well.
Stir in the flour, baking soda and oats. Mix just until combined.
Spread in an 8x8 pan that has been sprayed with cooking spray.*
Bake at 350 degrees for 23-25 minutes.
Allow the bars to cool. After the bars have cooled to room temperature, spread ¾ cup creamy peanut butter overtop the oatmeal bars.
Pour 1 1/2 cups water in the bottom pan of a double boiler and heat over medium-low heat.
Place the heavy whipping cream in the top pan of the double boiler.
Heat the heavy whipping cream until it is hot and steaming, but not boiling.
Remove the top portion of the double boiler from the heat and place it on a hot pad.
Add the chocolate chips.
Cover the pan with a plate and let it sit for 2 minutes.
Remove the plate and stir the chocolate for 1-2 minutes or until it is smooth and shiny.
Allow the ganache to sit for 3-5 minutes to cool just a bit.
Using a rubber spatula, spread the ganache overtop the peanut butter in a smooth layer.
Garnish the top with buckeyes while the chocolate is still wet if you desire the buckeyes to stick on the bars.
Cut into 9 bars and store in an airtight container.
*If you’d like to easily remove the bars from the baking pan to cut clean squares, first line the 8x8 pan with a piece parchment paper large enough to cover the bottom and hang over the sides of the pan about 1 inch. Then press the dough onto the parchment paper and bake as described. I like to remove the bars from the pan before I add the peanut butter and ganache toppings. This allows me to get the toppings all the way to the edges and cut the bars evenly.**You can also make ganache in the microwave. Simply warm the heavy whipping cream in a microwave safe bowl, 20 seconds at a time, stirring between each interval, until the cream is hot but not boiling. Then add the chocolate chips and cover with a plate. Continue as described above.***This amount of chocolate chips and cream makes a thick layer of ganache for the tops of the bars. If you’d like a thinner layer, simply use 1/4 cup heavy cream and 1 cup of chocolate chips.****The calories shown are based on the bars being cut into 9 pieces, with 1 serving being 1 bar. These bars are big and rich, so if you cut them smaller, they will be less calories! Since different brands of ingredients have different nutritional information, the calories shown are just an estimate.