01 - Preheat oven to 400°F. Line baking sheet with parchment paper.
02 - Roll puff pastry onto prepared sheet. Fold edges inward to create 1-inch border. Prick base thoroughly with fork.
03 - Bake pastry 10 minutes until lightly golden. Remove from oven and press down any puffed areas to create flat base.
04 - Whisk eggs, milk, cream, Dijon mustard, salt, pepper, and smoked paprika in large bowl until completely smooth and well combined.
05 - Distribute cooked bacon, spinach, tomatoes, and spring onions evenly over pastry base. Sprinkle cheddar cheese across vegetables.
06 - Pour egg mixture gently over fillings, spreading evenly. Return to oven and bake 25 minutes until center is just set and top is golden brown.
07 - Cool tart 5 to 10 minutes before slicing. Garnish with chopped chives. Serve warm.