Line two baking sheets with parchment paper or a silicone baking mat (see note). Preheat the oven to 350 °F.
Cream the butter, sugar and half the orange zest until light and fluffy.
Scrape the bowl. Add the orange juice, orange extract and vanilla, mix until well combined. Add the egg and mix until well combined. Scrape the bowl.
Add the salt, baking soda and flour and mix until incorporated.
Use a pastry bag fitted with a 1/2" plain tip to pipe 3" long cookies. Alternately, use a .75 oz scoop or a tablespoon to scoop the cookies onto the prepared baking sheets, leaving 2" between the cookies. They will spread as they bake.
Bake until the edges are golden brown and the middle of the cookies are set, about 8-10 minutes. Transfer the cookies to a cooling rack and allow to cool completely.
While the cookies are cooling, melt the chocolate in a microwave or over a double boiler. Stir the remaining orange zest into the melted chocolate.
Pair the cookies up by size and shape. Use a small spatula to spread a thin layer of melted chocolate onto the flat side of one cookie in each pair.
Sandwich the cookies and allow the chocolate to set.