Preheat the oven to 350F.
Line a baking sheet with non-stick paper.
Sift together the flour, starch, salt and vanilla seeds in a bowl.
In another bowl, whisk the softened butter and powdered sugar until smooth.
Add the flour mixture and mix until you have rather stiff dough which should be smooth, not crumbly. If the mixture appears crumbly, add 1 tbsp. of milk and mix. Otherwise, you can skip the milk altogether.
I used a piping bag to shape the cookies. You don’t have to; you can use a small scoop or just drop the dough by teaspoonful on the baking sheet. If you use a piping bag, however, there are more options. You can create large and flatter cookies or small plump ones depending on the tip that you use. Whether you use a piping bag or not, remember to place the cookies at least an inch and a half apart as they will spread.
Bake at 350F for 12 to 15 minutes, or until the edges are lightly browned.
Leave on the baking sheet for at least three minutes before moving to a wire rack to cool completely.
You can sprinkle the cookies with a little cocoa powder and powdered sugar before serving.