Preheat oven to 350 degrees F.
Line 2 baking sheets with parchment paper. Set aside.
In medium bowl, whisk together flour, baking soda, and salt. Set aside.
In large bowl with an electric mixer, beat together the butter and 1 1/2 cup sugar until light and fluffy, 2-3 minutes.
Add in egg, vanilla extract, and vanilla seeds and mix until smooth, scraping down the sides of the bowl to make sure everything is combined.
Reduce speed of electric mixer to low and gradually mix in flour mixture.
Scoop batter by the tablespoon and space at least 2 inches apart on prepared baking sheets.
Bake in preheated oven for 10-12 minutes.
If you are baking two sheets at a time, make sure to rotate the sheets halfway through baking time, about 5 minutes.
To make the filling, puree the raspberries and remaining 2 tsp sugar in a food processor.
Pour mixture through a fine sieve over a small bowl.
Press the juice through the sieve, leaving the seeds behind.
This may take a few minutes, to get all of the juice through. Set mixture aside and discard seeds.
Melt white chocolate in a heatproof bowl over a pan of simmering water.
Stir continuously until smooth, then remove from heat.
Slowly whisk in cream, followed by the raspberry mixture.
Refrigerate for at least an hour before filling the cookie sandwiches.
To make the sandwich cookies, spread raspberry cream on undersides of half the cookies, then sandwich them with one of the remaining cookies.