In large mixing bowl, use stand or hand mixer to whip butter, sea salt, coconut sugar and vanilla extract until well combined.

Add flour, cocoa powder and egg. Mix until well combined and crumbly. Use hands to roll mixture into ball. Refrigerate for 30 minutes to firm.

Preheat oven to 325 degrees F. Transfer cookie ball parchment-lined baking tray. Layer another sheet of parchment paper on top. Use rolling pin to flatten ball until it’s about 1/2-in. thick. Use small round cookie cutter to cut out cookies.

Transfer rounds to parchment-lined baking tray and bake 15-20 minutes. Remove from oven and allow cookies to cool completely.

In mixing bowl, combine all ingredients. Use spatula to mix and fold until well combined. Transfer to piping bag with a round tip attachment. Pipe a generous glob onto each cookie and cover with another cookie to form sandwiches.

Transfer cookies to refrigerator for 15-20 minutes to firm.