Preheat oven to 425°F, and grease 4 6-ounce ramekins with melted butter, making upward strokes along the sides. Coat with the crushed pistachio, shaking to remove any excess. Place ramekins on a baking sheet and set aside.
In a medium bowl (if using a hand mixer) or bowl of a stand mixer fitted with a whisk attachment, whisk egg whites on medium speed until foamy. Increase speed to medium-high and slowly sprinkle in granulated sugar. Continue beating the egg whites until glossy with soft peaks.
Add raspberry puree and corn starch to the egg whites and fold in gently until uniform in color / no streaks remain.
Pour or pipe the mixture into the ramekins, starting in the center (otherwise the pistachio will stick to the mixture and mix in), all the way to the top. Use an offset spatula to smooth the tops, and then use a paper towel (or your finger) to remove any excess batter from the sides/edges. Taking a small amount off the edge at the top can help the soufflés rise evenly.
Bake for 10-12 minutes, or until golden brown on top. Remove, dust with raspberry powder, garnish with raspberries, and serve immediately with melted (or frozen) vanilla bean ice cream.