In a large bowl with a hand or stand mixer, cream together butter, cream cheese, and sour cream just until light and fluffy, about 1 minute. Add in vanilla bean and sugars, and mix until combined. Then add in flour. Mix just until all ingredients are combined.

Divide dough into four equal balls and flatten into disks. Dough may be slightly sticky. Wrap each one with saran wrap and chill for two hours or overnight. Dough can also be frozen for up to 3 months.

When ready to bake, combine filling- remaining cream cheese, powdered sugar and salt in a medium bowl with a spoon or hand mixer.

Roll out each ball one at a time on a lightly floured surface into an 8-inch circle. Make sure circle isn't sticking as you roll it out so you can flip it. The sprinkle evenly with rainbow sprinkles and roll out circle into a 9-inch circle about 1/8 inch thick in order to secure sprinkles into dough. Throw some sprinkles in the air. Trust me, it's fun! Then carefully flip the circle over so sprinkles are on the bottom of the circle.. Keep the other balls refrigerated until you are ready to use them.

Spread about ¼ of filling onto the circle. Sprinkle evenly with MORE rainbow sprinkles. Heck yes.Cut the circle into 12 even triangles. Roll up each triangle from the wide end and secure the point into the cookie so you have a little spiral.

Whisk egg with 1 teaspoon water to make egg wash.Place cookies on a parchment lined cookie sheet point side down, glaze with egg wash, sprinkle with granulated sugar and refrigerate for 30 minutes. Repeat with other balls.