In KitchenAid mixer or with electric hand-mixer beat your butter until well-creamed.
Add sugar and cream together.
Stir in vanilla bean insides and vanilla bean paste.
Sprinkle in salt, stirring until well-combined, and scrape down the sides of the bowl using a rubber spatula to ensure ingredients are well-incorporated.
Add egg yolk and beat until combined (pausing again to scrape down sides of bowl).
With mixer on medium-low speed, gradually add flour until well-incorporated (you will need to scrape down the sides and the bottom of the bowl several times for this, as the mixture is fairly dry and crumbs tend to settle at the bottom of the bowl).
Transfer dough to clean surface and use your hands to form it into a cohesive ball.
Flatten into a disk (about 1" thick), cover with clear wrap, and chill for 15 minutes.
Preheat oven to 350F
Once dough has chilled, transfer it to a clean, lightly floured surface and use a lightly floured rolling pin to roll out to about ¼" thickness.
Lightly flour your cookie cutters and cut out your shapes, transferring them to ungreased cookie sheet, placing at least 1" apart.
Once you have cut out all of the shapes that you can, be sure to re-combine the scraps and roll out and cut out again to get the maximum number of cookies from your dough.
Bake on 350F for 9-10 minutes and allow cookies to cool completely before filling with chocolate cream.
Melt your chocolate and allow it to cool
In medium-sized bowl with an electric mixer, cream together butter and sugar until well combined.
Gradually add melted chocolate and stir until combined.
Stir in vanilla extract and salt.
Very slowly stir in heavy cream.
Gradually increase speed of mixer to medium, and then high. Beat on high speed for one minute. Scrape down sides of bowl and then beat on high for 30 seconds longer.
Use a knife or icing spatula to spread a dollop of frosting on the bottom of one cookie.
Sandwich with another cookie, and serve.
The cookie shells will soften the longer the cookies sit.