Be sure that the ingredients for the dough are at room temperature, as the dough needs to be soft enough to extrude easily from the pastry tip. The cookies can also be shaped with a cookie press.
In a bowl, whisk together the flour and salt. In a large bowl, using an electric mixer on medium-high speed, beat the butter and sugar until light and fluffy, 2–3 minutes. Add the egg and vanilla and beat on low speed until the egg is completely incorporated. Beating on low speed, slowly add the flour mixture and continue to beat unt