To make the peanut butter oatmeal base:

Preheat the oven to 350 degrees. Grease a 13"x9"x1" (you can also use a 13"x9"x2" pan) pan with cooking spray, cover in parchment paper, and spray again. Set aside. Place the oatmeal in a large mixing bowl and set aside.

In a medium sauce pan, over medium heat, combine the butter, peanut butter, sugar, corn syrup, vanilla and salt and stir gently until the butter, sugar and peanut butter melt and the mixture just begins to boil. Remove the mixture from the heat and pour the mixture over the oatmeal, scraping the sauce pan with a rubber spatula.

Fold the mixture into the oats, until it is all evenly coated. Transfer the coated oatmeal to the prepared baking pan. Press down (gently) on the base with your hands (or the bottom of a one cup dry measuring cup), flattening the oats, moving them into the corners of the pan, and ensuring that they are in a solid, even layer. Place the pan in the preheated oven and bake the oatmeal base for 10 to 12 minutes, or until the edges of it begin to bubble. Let the base cool on the counter while you prepare the ganache topping.

To make the milk chocolate peanut butter ganache:

Place the chocolate, peanut butter, and corn syrup in a small heat proof bowl. Pour the cream into a small sauce pan and heat it over medium to medium high heat on the stove top until bubbles form around the edges and just begin to form in the middle. Pour the warm cream over the chocolate and peanut butter and let the mixture sit for one minute. With a fork or small whisk, stir the mixture until the chocolate and peanut butter are completely melted. This may take more stirring than you'd think, but keep going until there are no more chunks of chocolate.

Pour the ganache over the baked oatmeal base. Using a small offset spatula, spread the ganache smoothly and evenly over the oats. Place the pan in the fridge for at least an hour or two, until the outside of the pan feels quite cold. When ready to serve the treats, sprinkle flaky sea salt over the ganache, and slice into whatever size treat suits your fancy. The treats will keep, covered in saran wrap and in the fridge, for 3 to 5 days, and can be frozen for up to one month.