Leek & Potato Galette with Pistachio Crust

DOUGH ½ cup raw pistachios 2 ½ cups all-purpose flour 1 t salt 1 t sugar 1 cup (2 sticks) chilled unsalted butter, cut into pieces FILLING & ASSEMBLY 1 T olive oil, plus more for drizzling 1 large leek, white and pale-green parts only, halved lengthwise, thinly sliced 4 ounces fresh goat cheese or feta if you prefer 5 T thick cream 2 garlic cloves, finely chopped Salt, freshly ground pepper All-purpose flour (for surface) 4 T coarsely chopped dill, divided, plus sprigs for serving 2 large potatoes, thinly sliced 1 large egg, beaten to blend Crushed pink peppercorns...