Preheat the oven to 325 degrees.. Line four baking sheets with parchment or silicone baking mats.
In a medium bowl using an electric mixture, beat the butter, cream cheese and granulated sugar on medium-high speed until light and fluffy.
Add the vanilla and eggs (one at a time), and beat to combine. With mixer on low, gradually add the flour and salt, and beat until just combined.
Transfer the batter to a piping bag or zip-top bag. Fit the piping bag with a large plain tip (½-¾ inch), or snip a ¾-inch hole in one corner of the zip-top bag. I strongly recommend using a proper piping bag and tip.Holding the bag at about a 90 degree angle, pipe cookies that are four-inches long and at least 1½ inches apart onto baking sheets.
Bake 18-20 minutes, until the cookies are light golden at edges, rotating sheets halfway through baking. Transfer to wire racks, and let cool.
Frosting
Melt the chocolate in a glass bowl in the microwave for about 1½ minutes, stirring every 30 seconds, until smooth.
With a small spoon or offset spatula, spread the melted chocolate on flat side of half the cookies. Top the chocolate-covered cookies with the remaining half of the cookies. Cookies can be stored in an airtight container up to a week.