Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.

Beat in the eggs one at a time, then stir in the vanilla extract.

In another bowl, whisk together the flour, baking soda, cinnamon, and salt. Gradually add this mixture to the wet ingredients, stirring until just combined.

Gently fold in the rolled oats until everything is evenly mixed.

Use a cookie scoop or tablespoon to drop rounded balls of dough onto the prepared baking sheets, leaving space between each one.

Bake in the preheated oven for about 10-12 minutes or until the edges are light golden brown.

Let cool on the baking sheets for a few minutes before transferring to a wire rack.

In a separate bowl, beat together the marshmallow fluff and powdered sugar until smooth and creamy.

Once the cookies are cool, spread cream filling on the flat side of one cookie and top it with another cookie, pressing down gently.

Enjoy your Homemade Oatmeal Cream Pies!