After preheating the oven to 350 degrees Fahrenheit, add the softened butter, brown sugar, and granulated sugar to your stand mixer. Cream with the paddle attachment, scraping down the sides occasionally.

Add in eggs one at a time, followed by vanilla and sourdough discard. Mix well.

In a separate bowl, mix oats, flour, baking soda, baking powder, cinnamon, and salt. Add the dry ingredients to the wet ingredients about 1/3 at a time, mixing after each addition. Don't over mix.

Prepare parchment paper-lined baking sheets, then scoop approximately 36 cookies onto the trays spaced about 2" apart. Bake for 10 minutes. The edges will turn golden brown, but the middle will still look a bit underdone.

After removing from the oven, leave the cookies on the trays for two minutes more before transferring to a cooling rack.

While the cookies cool, prepare the frosting. Give your stand mixer bowl a quick wash, then add the room temperature butter and cream cheese. Cream with the whisk attachment.

Add vanilla and salt, then slowly add powdered sugar with the mixer on low speed. Once all the sugar is added, whip at medium-high speed until fluffy.

Use a piping bag or small offset spatula to spread the frosting onto the flat, bottom side of a fully cooled cookie. Place another cookie on top of the frosting, making a sandwich. Assemble the rest of the cookies into cream pies and enjoy!