In a medium bowl whisk together the flour, salt, baking powder, baking soda, and cornstarch and set aside.
In a large bowl using an electric mixer cream the butter and sugar until fluffy (5 minutes or so).
Add in the egg, vanilla, and almond extract.
Next mix in the sour cream.
Add the flour mixture to the wet mixture and mix until everything is just combined.
Shape the dough into a disk, wrap in plastic wrap and refrigerate for at least an hour.
Preheat your oven to 375 degrees.
Roll the dough out to about a ¼ inch then use a 3 inch circle cookie cutter to cut the cookies.
Place the cookies on a parchment lined cookie sheet and bake for 8-9 minutes.
You do not want to overbake these cookies, they should have barely any color on them.
Let the cookies cool completely.
For the buttercream using an electric mixer cream the butter until fluffy and add in the powdered sugar and vanilla.
Next add in the milk. You may need to add just a little extra milk to get the consistency right.
Separate the buttercream into 3 bowls and use the food coloring to dye each one.
Frost the cookies using a piping bag or offset spatula.
Top with halloween sprinkles and serve!