For the Lavender Sugar

1. In the bowl of a food processor, combine the granulated sugar and dried lavender. Pulse several times until the lavender buds are fine.
2. Set aside. 

For the Cookies

1. In a large mixing bowl, add the butter and sugars. Using a hand mixer, mix until light and fluffy, about 3 minutes. 
2. Add the egg yolks and vanilla bean paste; mix until incorporated. 
3. Scrape the sides and bottom of the bowl with a spatula to ensure the last 2 ingredients are mixed in.
4. Add the flour and salt into the bowl all at once. With the mixer on low speed, gently blend in the flour until it is absorbed and large crumbles have formed. Stop mixing and avoid mixing past this point as it will result in tough cookies. 
5. Lay down a piece of plastic wrap and begin to shape the dough into a long log, about 2 inches in diameter. 
6. Wrap the dough in plastic wrap and roll it back and forth on the surface to even out the edges of the dough, creating a rounded shape. 
7. Freeze the cookie dough log for 1-2 hours. 
8. When ready to bake, preheat the oven to 350ºF and prep 2 baking sheets with parchment paper.
9. Slice the cookie log into 1/4" thick slices and arrange them on the baking sheet leaving at least 1.5" of space in between. Reshape the edges of each cookie into circles as needed. 
10. Sprinkle the tops heavily and generously with sparkling sugar. 
11. Bake the cookies for 10-13 minutes until lightly golden brown on the edges.
12. Allow to cool on the baking tray for a couple of minutes before transferring to a baking rack to cool completely.
13. Store in an airtight container for up to 5 days.