Preheat the oven to 350 degrees F. Line two baking sheet with parchment paper.
Mix together the flour and salt. Set aside.
Cream the butter and powdered sugar together until light. Beat in the eggs well Add in the vanilla and the melted butter and mix until well combined. Add in the flour mixture and mix until just combined.
Fit a piping bag with a large ½" round piping tip and fill with the cookie dough.
Pipe 2-inch lines of dough two inches apart on the parchment paper. Bake for 9 - 10 minutes, or until the edges are golden brown.
Turn off the heat and crack open the oven, and leave the cookies there to crisp for about 10 - 20 minutes, keeping an eye on them so they don't get too dark at the edges.
Allow to cool completely.
While the cookies are baking, heat the chocolate and heavy cream over a double boiler until smooth. Allow to cool completely.
Drop a teaspoon of the ganache onto half the cookies and top with the other half of the cookies. The ganache will harden over time.
Store in an airtight container for up to 5 days.
Notes
If you want to make mint milanos, add a couple of drops of mint extract to your heavy cream before making the filling!