In a medium-sized mixing bowl, beat brown sugar, white sugar, and butter until light and fluffy.
Mix in eggs one at a time until fully combined.
Mix in salt, cinnamon, baking powder, heavy whipping cream, baking soda, and flour until just combined.
Fold in oats and chocolate chips.
Scoop out golf ball-sized balls of dough and set them on parchment- or Silpat-lined cookie sheets spaced about 2" apart from each other.
Bake for 10 minutes or until they are lightly browned around the edges.
Cool on a cooling rack.
Filling Instructions
Beat butter for two minutes on high speed in the bowl of an electric mixer.
Add powdered sugar and beat for another two minutes. It's important to beat for a long time in order to incorporate a lot of air and to end up with the fluffy texture that we are looking for.
Mix in heavy whipping cream, vanilla bean paste, and salt and beat for another minute.
Sandwich spoonfuls of filling between pairs of cooled cookies.