Combine flour and salt in a bowl. Cut in cold cubed butter with a fork until mixture resembles coarse crumbs. Gradually add ice water and stir until dough just comes together. Knead 3-4 times, wrap in plastic wrap, and chill in refrigerator for 30 minutes.
2 cups all-purpose flour, 1 tsp salt, 0.5 cup butter, 0.5 cup water
Heat a skillet over medium heat and sauté diced onion for 8 to 10 minutes until translucent and slightly caramelized. Drain any excess liquid. Transfer onions to a bowl, let cool 5 minutes, then stir in shredded cheddar, black pepper, and optional mustard powder.
1 large yellow onion, 1.5 cups sharp cheddar cheese, 0.5 tsp black pepper, 0.25 tsp mustard powder
Roll chilled dough on a floured surface to ⅛-inch thickness. Cut into four 6-inch circles using a plate as a guide. Place one quarter of filling on one half of each circle, leaving a ½-inch border. Brush edges with water and fold dough over to form half-moons. Press edges firmly with a fork to seal.
2 cups all-purpose flour, 1 large yellow onion, 1.5 cups sharp cheddar cheese, 0.5 tsp black pepper, 0.25 tsp mustard powder
Preheat air fryer to 350°F for 3 minutes. Cut parchment paper squares to place under each pasty. Brush the tops of pasties lightly with beaten egg for a golden finish. Place pasties in air fryer basket, spaced 1-2 inches apart.
1 egg egg
Cook at 350°F for 7 minutes, then carefully flip pasties with tongs. Cook for another 7 to 8 minutes until pastry is golden brown and crispy. Check edges are sealed with no leaks. Let rest 3 to 4 minutes before serving.
1 egg egg
