Combine the dry ingredients in a bowl and stir them together.
Cream the butter and sugar until light and fluffy. Add the eggs, then the vanilla and beat until combined. Finally add in the dry ingredients.
Using a medium cookie scoop, measure out the cookies onto a sheet lined with either parchment paper or a silicon mat.
Put a small amount of sugar into a bowl, press the bottom of a glass into the sugar and slightly flatten the cookie.
Bake at 350℉ for 15 minutes. The edges should be slightly firm, but soft in the middle. Press more sugar into the top of the cookie flattening it a bit more with a glass.
Transfer to a cooling rack to cool completely.
Combine all ingredients for the filling in a mixer on medium speed. Sandwich the filling and cookies and enjoy.