Preheat the oven to 350 degrees F. Line a large baking sheet with parchment paper.
In a medium bowl, whisk together flour, oats, baking soda and salt. Set aside.
In the bowl of an electric mixer, add in softened butter, peanut butter and brown sugar; mix on medium low until well combined. Switch mixer to low speed; add in egg, vanilla extract, honey and sour cream and beat for 1 minute or until well combined, smooth and creamy. Slowly add in dry ingredients, increasing speed to medium low; mix until just combined. If you want to add in chocolate chips, now is the time to do so. I suggest mini chocolate chips!
Use a small cookie scoop to grab a tablespoonful of dough and roll into a ball with your hands. It’s important that the dough is smaller as the cookies will expand and since we’re making sandwiches, you don’t want them too big.
Place dough on the cookie sheet lined with parchment paper, leaving 2 inches apart between each dough ball. Bake for 10-12 minutes or until the edges are just barely golden brown. A slightly underbaked cookie is always best so they stay nice and chewy!
Allow cookies to cool on the cookie sheet for 5-10 minutes before removing and transferring to a wire rack. This allows them to set up a bit and harden slightly around the edges. Repeat with remaining dough.
Once cookies have cooled completely, you can make the peanut butter filling: in the bowl of an electric mixer, add the softened butter and peanut butter and whip on high until light and fluffy. Add powdered sugar, vanilla and 1 tablespoon of milk. Beat slow at first, then increase speed to high and beat for approximately two minutes. Frosting should be nice and creamy, if you want it extra creamy, add another splash of milk and beat again.
Top one cookie sandwich with a spoonful of filling, leaving a nice edge around the cookies and top with another cookie sandwich, then very gently press down slightly. Repeat with all cookies. You should get about 16 oatmeal cream pies. The filling will have the best texture after letting the cookies sit at room temperature for 1 hour, if you try to bite into them earlier the frosting won’t be as firm as we’d like. Makes 32 cookies, 16 oatmeal cream pies