Sauté the onion in a little butter and add the spinach. Squeeze spinach and onion well in a sieve and marinate with juice of one lemon, add 1/4 of lemon zest.
Lay out Parma ham on parchment paper. Place cheese on top and spread lemon spinach and finely chopped dates evenly on top. Roll up, turn in flour to other side and pull through beaten egg, then turn in bread crumbs to other side and toast in olive oil.
Blueberry sauce: whisk together all ingredients except blueberries, then fold in pureed blueberries and whole berries and season with salt.
The dish goes well with a finely sliced roasted potato.
Tip: Did you know that one bowl of spinach already covers the entire daily requirement of vitamin K and beta-carotene?