pistachio cinnamon sugar filling:

1. In the bowl of a food processor, add sugar and orange zest and blend until well mixed. Add salt, cinnamon and pistachios and pulse until nuts are finely ground. Transfer to a bowl and set aside.

sourdough crepes:

1. Combine starter, eggs, sugar and salt in a blender and blend on high speed until smooth, about 30 seconds. With the blender running on low, slowly drizzle in 2 tablespoons of melted butter and blend until combined.
2. Heat a 7- to 8-inch nonstick pan over medium heat. Use a pastry brush or paper towel to coat the pan with a thin layer of remaining melted butter. Ladle in 2- 3 tbsp of batter and quickly swirl the pan to cover the bottom with a thin, even layer of batter. Cook for about 1 minute, or until the edges are golden brown. Carefully flip the crepe and cook another 20- 30 seconds, or until the bottom is browned in spots. Repeat buttering, swirling and flipping crepes, adjusting heat as necessary (see notes above for tips).
3. Store on a plate, covered with plastic wrap or a clean linen to stay warm and moist.
4. To serve, spread a crepe with softened butter. Sprinkle the surface with pistachio cinnamon sugar. Fold crepe in half, then in half again and serve while still warm.