In a large mixing bowl, combine neutral cooking oil, honey, and lye water if using, along with a pinch of salt. Gradually fold in cake flour until a soft dough forms. Knead the dough gently for a couple of minutes until smooth. Cover the bowl with a damp cloth and let it rest for 1 to 2 hours at room temperature.

While the dough rests, preheat the oven to 350°F. Spread shelled pistachios on a baking sheet and toast for about 8-10 minutes until fragrant. In a separate bowl, combine the toasted pistachios, glutinous rice flour, honey, granulated sugar, salt, and enough water to bind the mixture into a cohesive filling. Divide this filling into 10 equal pieces and shape each into a smooth ball.

After resting, knead the dough briefly and divide it into 10 equal portions. Roll each piece into a ball and then flatten it into a small disc, creating a well in the center for the filling. Place a ball of pistachio filling into the well and carefully fold the dough around it, sealing the edges smoothly.

Dust a mooncake mold with flour to prevent sticking, then press each dough ball gently into the mold to shape it. Tap out the mooncake onto a lined baking tray. Mist the tops lightly with water. Bake in the preheated oven at 350°F for 10 minutes, then remove and let them cool slightly.

Once cooled, prepare an egg wash by beating the egg yolk. Brush a thin layer over the top of each mooncake. Return them to the oven and bake for an additional 5 to 8 minutes until they achieve a deep golden color.

Once baked, allow the Honey Pistachio Mooncakes to cool completely on a wire rack. Store the cooled mooncakes in an airtight container at room temperature for 2 to 3 days.