Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius).

Line your baking sheets with parchment paper.

In a medium bowl, whisk together the rolled oats, flour, baking soda, salt, ground cinnamon, nutmeg, and ground ginger (if using). Set this mix aside.

In a large mixing bowl, use an electric mixer to cream together 1 cup of unsalted butter, granulated sugar, and brown sugar until fluffy.

Blend in the molasses, egg, egg yolk, and vanilla extract until well combined.

Slowly mix in the flour and oat mixture until just combined, being careful not to overmix.

Scoop out dough onto the prepared baking sheets and flatten each scoop slightly with your fingers.

Bake for about 9 minutes, or until the edges are lightly golden.

Remove the cookies from the oven and let them cool on wire racks.

In a medium bowl, cream together 8 tablespoons of unsalted butter and the cream cheese until smooth.

Add in the powdered sugar and 1 teaspoon of vanilla extract, whipping until fluffy.

Spread or pipe the filling between two cooled cookies to make a sandwich.