Place 1/2 ounce of freeze-dried raspberries in a plastic bag. Lightly tap the bag with rolling pin until the freeze-dried berries are broken up into the size of small beads. You don't want to turn the berries into a powder. Set the berries aside.
Place the butter, sugar, and salt in the bowl of a stand mixer with the paddle attachment and mix on medium speed until the mixture is smooth about 2 minutes. Stop the mixer, scrape the sides and bottom of the bowl.
Add the egg and vanilla extract and mix the dough on medium speed just until the egg is mixed in.
Add all of the flour at once, turn the mixer to low speed and mix until all the flour is mixed in and the dough is soft but still slightly crumbly. Scrape the sides and bottoms of the bowl. Add the freeze-dried raspberries and mix on low speed until the berries are barely mixed into the dough. The dough will be marbled red and white with visible bits of freeze-dried berries.
Turn the cookie dough out onto a lightly floured surface. You can also use a large piece of parchment paper or Silpat.
Use your hands to shape the dough into a rectangle and lightly flour (just a sprinkle) the top of the dough. Do not use too much flour, just enough to keep the rolling pin from sticking.
Roll the dough out to 1/4-inch thick. Use a 2-inch or 3-inch heart-shaped or round cookie cutter to cut out the cookies. Place the cookies on a parchment-lined cookie sheet about 1-inch apart.
Reroll the cookie dough and continue to cut out cookies until all the dough has been used. You might have a small piece left over.
Chill the dough in the refrigerator for at least 20 minutes. Chilling the dough will help the cookies hold their shape when baking.
While the cookies are chilling preheat the oven to 300 degrees F and line a half baking sheet with parchment paper.
Bake the cookies for 20-25 minutes. The bottom of the cookies will be lightly golden brown. 2-inch cookies will usually take 20 minutes and 3-inch cookies 25 minutes.
Take the cookies out of the oven and allow them to cool for about 5 minutes on the cookie sheet before moving them to a cookie rack to completely cool.
The shortbread cookies can be stored in an airtight container for 1 week.