1/2 cup unsalted pistachios, shelled and roughly chopped
3 tablespoons cacao nibs or chocolate chips
Line a rimmed baking sheet with parchment paper. (The size of your sheet will determine the thickness of the bark.)
Combine the yogurt, sugar, half of the raspberries and half of the pistachios in a large bowl. Pour the mixture onto the prepared sheet and smooth out the surface. Sprinkle the cacao nibs, the remaining half of the raspberries and the remaining half of the pistachios across the surface.
Freeze until completely firm, 3 to 4 hours. Use a mallet or the back of a wooden spoon or rolling pin to break the bark into smaller pieces. Store in the freezer.