01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - Roll out the puff pastry onto the prepared sheet, folding the edges inward to create a 1-inch border. Prick the base with a fork.
03 - Bake the pastry for 10 minutes until slightly golden. Remove from the oven and gently press down any puffed areas.
04 - In a large bowl, whisk together eggs, milk, cream, Dijon mustard, salt, pepper, and smoked paprika until smooth.
05 - Scatter cooked bacon (or mushrooms), spinach, tomatoes, and spring onions evenly over the pastry base. Sprinkle with cheddar cheese.
06 - Pour the egg mixture gently over the fillings, spreading evenly.
07 - Return to the oven and bake for 25 minutes, or until the center is just set and the top is golden.
08 - Cool for 5 to 10 minutes. Garnish with chopped chives, slice, and serve warm.