Adapted from Bake From Scratch, Edd Kimber. This recipe can also be made into slice and bake logs, but I chose to roll the dough and cut out squares.
Beat the butter until creamy. Scrape the sides and bottom of the bowl.
Add the powdered sugar in 3 additions, beating until creamy and scraping after each one.
Beat in the freshly ground coffee.
Scrape the sides and bottom of the bowl and add the egg yolks and vanilla bean paste. Beat until incorporated and once again scrape sides and bottom of bowl.
Whisk together the flour and salt and then mix it into the dough on the slowest speed.
When the dough is evenly mixed, divide it into 3 balls. Flatten those into discs and then wrap in plastic wrap. Chill for at least an hour.
When you are ready to bake, preheat the oven to 350 F.
Remove the discs one at a time (in other words, leave the dough chilling until you are ready to roll) and place in between 2 pieces of parchment or wax paper. Roll to 1/4-inch thickness and then cut into desired shape. We did squares for fun, but in hindsight I realized rounds would have been easier to fill because you can dollop some filling in the center of the cookie and then screw the 2 rounds together--squares and other cornered shapes are trickier.
Remove the cut outs to a parchment lined cookie sheet (or silicone mat lined) and place them 1 inch apart. I got 20 cookies to a sheet.
Quickly re-roll the cookie dough scraps and repeat. When the ball gets too small, add it to the next disc from the refrigerator and repeat until all of the dough has been used.
Bake the cookies for 10-12 minutes, until they are just lightly browning at the edges. Remove and let cool for 5 minutes on the pan before removing to cool completely on a cooling rack.
Using a double boiler or a heat-proof bowl in a pan of simmering water, melt the blonde chocolate with the coconut oil. Stir until melted, and then whisk in the sea salt.
Remove the chocolate to cool. When it has cooled and thickened a bit but is still pour-able, pour the chocolate either into a freezer plastic bag or a squeeze bottle designed for drizzling chocolate (do not use a traditional cake decorating bag as the chocolate will just run through the tip immediately).
Cut a tiny snip from the corner of the bag if you are a using a freezer bag. Drizzle the chocolate onto half of the cookies (bottom sides up). Work quickly because the chocolate sets quickly.
If you notice the chocolate setting before you create sandwiches, do this in batches. It will depend on the temperature of your kitchen. While the chocolate is still glossy and melted, place a second cookie, bottom side down, over the chocolate. Press just enough to set--you do not want chocolate dripping everywhere, and you want the filling in the cookie sandwich not squishing out of it. Separate the cookies so that none of them are connected if any white chocolate connects them.
Leave the cookies to set at room temperature before storing in airtight tins.
I love caramelized white chocolate; if you want to try making your own, I have instructions here in my Butterscotch Pecan Bundt Cake with Caramelized White Chocolate Glaze. If, like me, you conquered making it once and thought it was amazing but rarely find the time to make your own, or just don't want to bother, I recently discovered that Valrhona is selling blond chocolate feve discs. People this is not sponsored but it is an affiliate link and it is life changing!