01 -
Start by preheating your oven to 350°F and line your 18x13-inch baking sheets with parchment paper for perfect release.
02 -
In a mixing bowl, whisk together your oats, flour, baking soda, salt, cinnamon, nutmeg, and ginger (if using) for about 30 seconds until well combined.
03 -
Using either a hand mixer or stand mixer with paddle attachment, cream together 1 cup butter with both sugars until the mixture becomes pale and fluffy, about 2-3 minutes.
04 -
Mix in molasses, then add the egg, followed by the egg yolk and vanilla extract. Remember to scrape down the bowl between additions to ensure everything is evenly mixed.
05 -
Gradually add the flour mixture to your wet ingredients, mixing until just combined. Give the bowl a final scrape and fold to make sure everything is evenly incorporated.
06 -
Scoop 1 1/2 tablespoons of dough (a #40 scoop is perfect), place 12 cookies per sheet, slightly flatten each, and bake one sheet at a time for 9 minutes. The edges should be set but centers slightly underbaked.
07 -
Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
08 -
Beat together the softened butter and cream cheese until smooth. Add powdered sugar and vanilla, then whip on high speed for 2-3 minutes until light and fluffy.
09 -
Spread or pipe the cream filling between pairs of cooled cookies to create sandwiches.