Pulse pistachios in a food processor until coarsely ground. Add flour, salt, and sugar and pulse to combine. Add butter and pulse just until a coarse meal forms. Gradually stream in ice water and process until dough comes together. Transfer dough to a work surface; form into 2 balls, and flatten into disks. Wrap in plastic; chill at least 30 mins.

Preheat oven to 400º F. Heat oil in a small skillet over medium-low. Cook leek, stirring occasionally, until softened but without taking on any color, about 5 mins. Remove.

Mix goat/cream cheese, cream, and garlic in a bowl to combine; Salt and pepper to taste.

Roll out 1 piece of dough on a lightly floured surface to an 8-inch round; transfer to a parchment-lined baking sheet. Spread ½ of goat cheese mixture over dough, leaving a 1" border. Scatter ½ dill evenly over, then top with a thin layer of potato slices. Drizzle with oil; season with salt. Scatter ½ of leeks over potatoes. Fold edges of dough over filling, tucking and overlapping slightly as needed. Repeat for 2nd galette. Brush dough w/egg.

Bake until crusts are golden brown ~35 mins.