Making Homemade Oatmeal Cream Pies is simple if you follow these steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.
2. Cream Butter and Sugars: In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
3. Add Eggs and Vanilla: Beat in the eggs, one at a time, followed by the vanilla extract until well combined.
4. Mix Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, cinnamon, and salt.
5. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
6. Stir in Oats: Fold in the rolled oats and mini chocolate chips (if using) until evenly distributed.
7. Scoop the Dough: Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
8. Bake: Bake in the preheated oven for 10-12 minutes or until the edges are lightly golden. The centers may look slightly underbaked; this is okay as they will firm up while cooling.
9. Cool the Cookies: Remove from the oven and let the cookies cool on the baking sheets for about 10 minutes before transferring them to wire racks to cool completely.
10. Prepare the Cream Filling: In a medium bowl, beat the softened butter until creamy. Gradually add the powdered sugar, mixing until smooth. Add the vanilla extract and milk, adjusting the consistency as needed.
11. Assemble the Pies: Once the cookies are completely cool, spread a generous amount of cream filling on the flat side of one cookie, then sandwich it with another cookie.

These steps will guide you in creating delightful Homemade Oatmeal Cream Pies that everyone will love!