Perfect Beef Xian Bing (Chinese Meat Pie)

Name: Perfect Beef Xian Bing (Chinese Meat Pie)
Prep time: 30 min
Cook time: 20 min
Total time: 50 min
Cuisine: Asian, Chinese
Ingredients: 400 g all purpose flour (about 3⅓ cup loosely measured ); ¼ tsp sea salt; 250 g hot water (see note) (150°F/65°C, 1 cup + 1tbsp); 1 tbsp Sichuan peppercorn; ⅔ cup water; 1 lb ground beef (20-30% fat); 1 tsp freshly grated ginger; 2 tbsp soy sauce; 1 tbsp rice cooking wine (or Shoaxing wine); ½ tsp sea salt; ½ tsp sugar; ⅛ tsp white pepper powder; ¼ tsp freshly ground black pepper; 1 egg; 1 tbsp sesame oil; 2 scallion (chopped); vegetable oil