Grab a large mixing bowl, and prepare to measure out the dry ingredients:4 cups of rolled oats 1 cup of packed brown sugar Pile the oats into a clean mixing bowl with a measuring.  Unlike with flour, your measurements need not be super accurate. Pack 1 cup of brown sugar into the same measuring cup, and drop the sugar into the mixing bowl with the oats.  If you've never packed brown sugar before, it's pretty simple.  Pour or scoop some sugar into the measuring cup, and then press it down with your fingers until it feels firm.  Keep adding and pressing sugar until you get a 1 full cup of packed brown sugar leveled flat. Now that you have a mini sugar castle in the mixing bowl, break up the brown sugar, and begin stirring it in with the oats.  I find it helpful to start by pushing up the stuff on the bottom.  Keep stirring until only a few clumps of brown sugar remain.

Gather together the liquid ingredients:3/4 or 1 cup of softened butter - choose 1 cup if you want a gooey base1/2 cup of light corn syrup1 teaspoon of vanilla extract, if desired - for extra flavor To quickly soften butter straight from the fridge, unwrap the sticks (1-1/2 for 3/4 cup or 2 for 1 cup) into a microwave-safe bowl, and microwave on high for about 15 seconds.  After this, the butter should be easy to deform with your fingers but firm enough to hold its own shape.  Alternatively, you can leave the sticks unrefrigerated for 20 to 30 minutes, but you do not want them to melt completely. Add the softened butter to the bowl, and mix thoroughly.  It may take a few minutes of stirring, and even some "chopping" action with the mixing spoon, to get it completely mixed in with the dry ingredients.  If your guests won't mind, dive in with your fingers to make the process go faster. Measure out and pour in the corn syrup and vanilla.  After you stir the oatmeal mixture one more time, it will be ready for the oven!

If you haven't already, preheat the oven to 350 degrees F (180 degrees C).Read carefully!  Baking is the easiest part of this recipe to mess up because the oatmeal mix does not look much different when it is done in the oven.  Trust me, you don't want to burn these babies! A 9 by 13 inch pan is perfect for this recipe, but O'Henry bars are quite adaptable to whatever you want or need.  Feel free to use different pan sizes and types to get a dessert perfect for your occasion.  Want a bar that's extra thick and hearty? No problem; just watch the oven carefully.Generously grease all of the bakeware that you will be using with cooking spray.  There's no need to drench the pan, but using too little will make it challenging to get the bars completely out! Evenly press the oatmeal mix into a greased pan.  Traditionally, the base should be about 3/4 inch high.  Place the pan on the center rack of a conventional oven (remember hand protection).Bake for 10 to 15 minutes, or until the oatmeal just starts to turn golden brown.  Take the pan out of the oven, and set it out to cool.  While hot, the mix will remain as pliable as before.  Don't worry; it will become firm as soon as it cools. The bars are already delicious enough to eat, but the best is yet to come!

Making the chocolate-peanut butter topping is fast and fun! Find a small pot or saucepan and get the following ingredients:1 cup of semisweet chocolate chips 3/4 cup peanut butter In the cool pot, measure and add the chocolate chips and peanut butter.  Trying to measure and transfer the peanut butter may require a little patience but shouldn't be too much trouble with a simple butter knife. Set the pan on a burner set to low heat.  When I used natural gas burners, the chocolate began melting immediately.  Stir continuously to keep any of the chocolate from scorching.  The natural oils of the the peanut butter help prevent burning.  Very quickly, the chocolate chips melt and fuse with the peanut butter to make a chocolaty tonic worthy of Charlie's chocolate factory! Once the chocolate and peanut butter are completely mixed together, pour the topping immediately onto the cooling oatmeal base.  If you are sticking with time-tested tradition, gently spread the chocolate evenly with the flat of a large spoon.  I find it best to not be a perfectionist in this step because too much fussing with the spreading can cause the oatmeal to pull up and crumble, which does not look attractive. Even more so than with the oatmeal base, you can be as creative or picky as you like with the topping!  Pile it thicker an' deeper or elegantly drizzle it across.  You may also wish to try different ratios of peanut butter and chocolate.  If you run out of topping, it's a snap to whip up some more.

The O'Henry Bars are nearly ready to be devoured, but they are best served chilled.  Refrigerate them for at least an hour, or, in a pinch, put them in a freezer for a fraction of the time. Allow them to warm up for a little bit before cutting into them.  Slice them into pieces (a normal butter knife will do) into whatever serving size you wish.  Be sure to cut the pieces well, so that they will effortlessly pull away from the pan.Serve and enjoy!! O'Henry Bars travel well in tupperware containers.  Keep them covered to prevent dryness.