Preheat the oven to 200C/400F.
Add a drizzle of oil to a large pan over medium-high heat then add the beef. Break it up with your wooden spoon and when it begins to brown, stir in the taco seasoning and continue frying until the beef is cooked through. Add the tomato puree and water and continue frying for another minute or so until the water soaks up and the beef is nice and thick/juicy. If you have time, leave to cool, at least until it stops steaming.
Line 2 baking trays with baking paper. Slice one of the pastry sheets into 8 even-sized rectangles, then slice 2 more out of the second sheet (store the rest for a rainy day). Sprinkle the cheese in 10 mounds in the same shape as the pastry (just a teeny bit smaller) then top with the beef. Place the pastry over the top and press around the outside to secure the filling (doesn't have to be perfect) then brush with egg wash.
Bake in the oven for 15 minutes, or until deep golden and crispy. During this time you can prep the toppings and make the sauce by combining the sour cream and sriracha. The pastry should lift straight off the baking paper when you slide a spatula underneath. If for whatever reason it doesn't, you can cut around each pastry then individually flip them over and remove the paper.
Add the toppings and sauce then tuck in and enjoy!
