How to Make It
Preheat oven to 350°. Line 18 standard-sized muffin tin cups with liners.
Place the freeze dried blueberries into the bowl of a food processor; pulse until berries are ground into a powder. Whisk together the blueberry powder, flour, baking powder, and salt in a large mixing bowl. (Whisk thoroughly) as the freeze dried berry powder has a tendency to clump. Add the blueberries to the flour mixture and toss gently to combine.
Combine the sugar, egg, and egg yolk in a medium mixing bowl; beat vigorously with a whisk until incorporated and pale. While whisking, slowly pour in the melted butter, mixing until incorporated. Gently whisk in the sour cream.
Add the sour cream mixture to the flour mixture; gently fold using a rubber spatula until batter forms and no large pockets of flour remain. Divide the batter evenly among the muffin cups. Bake 25-27 minutes or until the muffins are beginning to brown and a toothpick inserted into the center of muffins tests clean, rotating halfway through baking.
Remove from oven and allow muffins to cool in the pan 5 minutes. Invert muffins onto a clean surface and stand them upright on a wire cooling rack; allow them to cool 15-20 minutes before serving.
In testing, we used a miniature food processor to grind the blueberries, but you could also place the berries in a plastic zip-top bag, seal, and crush using a heavy, flat-sided object, such as a mallet.