Bring a large pot of water to the boil and add the pasta shells, olive oil and a few pinches of salt.
While the pasta is boiling, make the béchamel sauce. Melt half (50g) of the butter in a saucepan over a medium heat, add the flour and whisk together to form a paste.
Allow to cook for a few minutes, until the mixture releases a slightly nutty aroma.
Steadily add the milk and continue to whisk vigorously to avoid any lumps forming. Allow the sauce to simmer, stirring constantly, until smooth and thick, then add the Cheddar and mozzarella and stir until the cheeses have melted.
Add the cayenne pepper and season to taste with salt and pepper.
Check on your pasta shells - they should be al dente (a little firm when you bite into one). Drain the shells in a colander and allow to cool.
In another pot, melt the remaining 50g of butter and gently fry the chopped onion until softened.
Add the mince, tinned chopped tomatoes, sugar and the contents of the sachet of KNORR Naturally Tasty Lasagne. Stir well and allow the mixture to cook through and reduce by half.
At this point, heat the oven to 180 °C.
Pour the béchamel sauce into a large serving dish and arrange the baby spinach leaves on top.
Fill each pasta shell with a tablespoon of the mince mixture and place the shells on top of the
Arrange the vine tomatoes on top of the shells and sprinkle the grated Grana Padano or Parmesan all over the top.
Bake at 180 °C for about 20 minutes, or until the dish is heated through and the cheese has melted.
Remove from the oven, garnish with micro herbs and serve immediately with a crisp green salad.