Homemade Oatmeal Creme Pies

In a small microwave-safe bowl, add the ½ cup unsalted butter (1 stick) and cover with a paper towel (will help for splattering). Melt the butter for 30-45 seconds until all is melted (no chunks left).

Pour melted unsalted butter into a larger bowl, then add in ¾ cup light brown sugar and ½ cup powdered sugar and use a spatula to stir until combined (it won't look totally smooth). Allow the mixture to cool for a few minutes until no longer hot (you don't want to cook the egg in the next step).

Add in 1 large egg and 1 teaspoon vanilla extract, then mix. Next, add in ¼ teaspoon baking soda, 1 teaspoon cinnamon, ½ teaspoon salt, 1 tablespoon cornstarch, and 1 teaspoon unsweetened cocoa powder and mix again.

In a food processor or blender, add 1 cup quick oats and ½ cup raisins and pulse until broken up (you want them coarse, not a fine powder). I did this for 10 pulses in my Ninja food processor.

Add oatmeal raisin mixture and 1 cup all-purpose flour to the dough, then mix until all the flour disappears into the dough. Add 2 tablespoons milk and mix until combined.

Line a baking sheet with parchment paper. 

Regular Sized: Scoop dough into 2-tablespoon sized scoop, roll into balls, then bake at 350℉ for 9-10 minutes. You want them look slightly underbaked, as they will continue baking on the pan (my oven was perfect at 9 minutes). This is important for a soft cookie!
Minis: Scoop into a heaping 1-tablespoon scoop, split in half, then roll into balls. Bake at 350℉ for 5-6 minutes.

Remove from oven and (if cookies have a slight puff to them) gently tap pan on counter to "deflate" cookies. Allow the cookies to cool on the hot pan for 10-15 minutes before removing them. This will allow them to finish baking on the hot pan.

Once cooled, use a knife or piping bag to pipe frosting in the center of one cookie then press another one on top to create a sandwich. If piping, don't pipe all the way to the edge to ensure the frosting doesn't squeeze out.