To make filling: put cream in a saucepan, add vanilla beans and boil. Put white chocolate in a pitcher and melt it in the microwave. Pour cream over melted chocolate, add butter and blend it with a blender until smooth for 1 minute minimum. Cover the plate with plastic, pour the filling, cover with plastic again and leave it in the fridge for 2-4 hours minimum. If you don’t, the filling will be too runny. The texture of the filling must be stabilized but stay soft and creamy. If your filling is runny and unstable, leave it in the fridge for more time.
To make dough for cookies: in a food processor mix butter, powdered sugar, two flours and one egg. Mix it until combined. Put dough between two sheets of parchment and roll it. Thickness should be 1/10". If cookies are too thick, you will not feel the taste of the filling. Leave it in the fridge for 30 minutes.
Take the dough out of the fridge and cut it out with a cookie cutter. Place the cutouts on a baking sheet with baking mat (or parchment) and leave it in the freezer for 30 minutes. Don’t skip this step. If you do, your cookies will melt in the oven and be not so beautiful. If you have two perforated silicone baking mats, you can use them: put one mat on a baking sheet, and cover cookies with a second one. Your cookies will be more crispy and beautiful, as in photos.
Preheat the oven to 320°F, take the cookies out of the freezer and bake until caramelized and golden. It will take about 20 minutes.
Transfer baked cookies to wire racks, let them cool. Take the filling out of the fridge and put it to a pastry bag, pipe it onto a cookie and form a sandwich. Leave sandwich cookies in the fridge just for 5-10 minutes and your super easy vanilla cookies are ready to enjoy! Store cookies in the fridge for several days.