Heat oven to 325°F (160°C).
Place freeze dried blueberries in a food processor and pulse until completely ground into dust. You can also place the blueberries in a resealable bag and roll with a rolling pin until completely ground into dust. Mix together blueberry dust, flour, oats, baking powder, and salt in a medium mixing bowl.
Using a stand mixer fitted with the paddle attachment, beat together butter, brown sugar, and granulated sugar on medium speed until light and creamy, about 2 - 3 minutes. Add in egg and vanilla extract and beat on low speed until incorporated.
With the mixer on low speed, add half of the dry ingredients and mix just until combined. Add remaining dry ingredients and mix together, scraping down the sides of the bowl as needed. The dough will be sticky. Add in ½ cup of white chocolate morsels and mix with a silicone spatula until combined.
Portion out the dough using a 3 tablespoon cookie scoop. Place the cookies 2 inches apart on a parchment-lined baking sheet.
Bake for 16 - 20 minutes until slightly golden brown around the edges and the middle of the cookies have set. Immediately once the cookies are removed from the oven and are still hot, grab a cookie cutter or cup a little larger in circumference than the cookie. Toss the cookie in the cookie cutter to shape the edges into a perfect circle. This helps fix any spreading that happens in the oven. Transfer to a cooling rack.
Once cookies are completely cooled, add the remaining ½ cup of white chocolate morsels and coconut oil to a small microwave-safe bowl. Microwave on 50 percent power for 30-second intervals, stirring in between each interval, until the chocolate morsels are fully melted. Using a spoon, drizzle melted chocolate over cookies in a decorative pattern. Allow the chocolate to fully dry on the cookies.
Store cookies in an airtight container at room temperature for up to 5 - 7 days.