In a grinder or food processor fitted with a blade, pulverize freeze-dried raspberries into a powder and set aside. In a medium sized bowl, sift together flour, baking soda, cream of tartar and salt and set aside.

With a hand or stand mixer fitted with a paddle attachment, beat room temperature butter and sugar together on medium until light and fluffy. About 3 minutes. Add egg, yolk and vanilla and mix for an additional minute.

In two additions, sift in the dry ingredients and mix just until combined. Do not overmix!

Divide the dough into two equal portions, placing one half into a small bowl. Sift raspberry powder into the bigger bowl and mix until just combined. Careful not to overwork the dough. Transfer the raspberry dough along side the vanilla dough (see photo).

Portion out your cookies using a small cookie scoop (#40 = 1 1/2 Tbsps). As you're scooping out your dough balls down the center, you can bring the sides of the dough towards the middle as needed to maintain consistency (see photo). Chill the cookie dough for at least 30 minutes or up to 3 days in the fridge before baking.

While the dough is chilling, set a rack in the center of the oven and preheat to 350ºF (180ºC). Before baking, you can optionally roll the dough balls into white sugar. Bake 6 to 8 cookies at a time in separate batches for about 10 to 11 minutes. You can keep the remaining cookie dough in the fridge while you're baking the cookies.

Let cool on cookie sheet for a minute and then gently press a white chocolate feve or disc on top of each cookie. Transfer to a wire rack to cool completely and enjoy! Keep in an airtight container at room temperature and enjoy for about 3 to 4 days!