• Preheat oven to 350°.
• Prep a template on parchment or wax paper for the cookies. Draw lines 2 inches long and set them 2 inches apart. Place this under another sheet of parchment paper to use as a guide as you pipe the cookies.
• In a mixing bowl, combine butter, sugar, and vanilla extract. Beat until light and fluffy. Scrape down sides and bottom of bowl and mix again, butter must be completely combined and smooth or cookies will "blow out" when baked.
• Add egg whites and beat until fluffy again.
• Add flour and salt, mix gently until just combined.
• Place a gallon ziploc bag inside a large glass and fill it with the cookie batter. Press out the air and seal the bag. Cut off one corner of the bag so that the opening is 1/2 inch wide.
• Pipe cookies onto clean piece of parchment paper, with the template underneath. Use a gentle pressure when piping so that lines are not too thick. They should be about 1/4 inch high off of the parchment.
• Taking opposite corners of the parchment, lift the cookies onto a baking sheet. Bake for 10-12 minutes, until edges of the cookies start to brown. Allow to cool completely on a cooling rack.
• Repeat until all batter is gone.

For Filling

• In a double boiler, melt dark chocolate and coconut oil together until completely smooth.
• Add peppermint essential oil to melted chocolate and mix well.
• Using a quart ziploc bag, fill bag with chocolate. Snip off 1/16 of the corner for piping.
• Pipe down the middle of a cookie 3-4x (depending on how much chocolate you want!), then place another cookie on top.
• Press the two halves together until chocolate is evenly spread.
• Repeat until all cookies are paired.