Start by preparing the crust. Mix the 2 cups all-purpose flour1/2 tablespoon salt 1/2 tablespoon English Mustard Powder (Colman’s), and 1/2 tablespoon Paprika, then cut in the 8 tablespoons butter until the mixture looks crumbly.
Add a beaten 1 large egg and 3–4 tablespoons of cold water, then knead until a soft, smooth dough forms. Wrap the dough tightly in cling film and refrigerate for 30 minutes.
While the dough chills, prepare the filling. Add 1 pound spinach, 1 large onion 1/2 tablespoon ground nutmeg, 1 teaspoon salt and 1 teaspoon black pepper to a pot and cook gently over medium heat with the lid on. Remove from heat and let cool slightly. Stir in 1 cup small curd cottage cheese, eggs (reserving one egg for brushing), 4 tablespoons Parmesan cheese, and 2/3 cup cream until well combined.
Take the pastry out of the refrigerator and roll it out. Line a 9-inch pie dish, crimp the edges with a fork, and prick the base all over. Place in an air fryer at 320°F for 8–10 minutes until lightly golden.
To bake in the oven instead, preheat to 375°F and bake the crust for 12–15 minutes until golden.
Spoon the filling into the prepared crust. Beat the remaining egg and brush it over the top. Return to the air fryer at 300°F and cook for 10–15 minutes until set.
For oven baking, place the filled quiche in a 375°F oven and bake for 25–35 minutes until the center is firm and the top is golden.
Let the quiche cool slightly before slicing so it sets properly and holds its shape.