Preheat the oven to 350˚F degrees. Mix together shortening and butter until combined.
Add the granulated sugar and brown sugar. Beat for 2-3 minutes.
Add eggs and vanilla. Beat for 1-2 minutes.
In a separate bowl, combine the flour, baking soda, ground cinnamon, and salt. Add to the mixing bowl and stir to combine.
Stir in the rolled oats.
Use a #40 dough scoop (about 2 tablespoons) to make dough balls. Place on parchment-covered baking sheets with at least two inches of space between balls of dough.
Allow the cookies to cool completely before storing them. Place the chewy oatmeal cookies in an airtight container (or ziptop bag) with pieces of parchment paper between layers. Store them at room temperature for 3-4 days. Or store them in the freezer for up to 4 weeks. Thaw them at room temperature before serving.
Oatmeal Cream Pie
First, make the fluffy buttercream frosting to use as a filling. Mix 1/2 cup of softened butter and 1/2 cup of shortening until smooth. Then, mix in 1/2 cup of marshmallow cream. Next, slowly stir in 2 cups of powdered sugar. Now mix in 1 teaspoon of vanilla extract and 2 tablespoons of mix. Then, stir in 2 additional cups of powdered sugar. Finally, beat the fluffy buttercream until smooth. Spread some frosting on the bottom of a cookie and top it with a second cookie. Gently squeeze the cookies until the frosting reaches the edges.Nutritional information was calculated for plain oatmeal cookies without glace icing or buttercream frosing.