Take the veal out of the fridge 30 minutes before starting to prepare it. Put the minced veal in a bowl. Peel the onion and chop finely. Mix the onion, mustard, paprika, eggs, breadcrumbs, parsley and Worcester sauce into the mince and season to taste with salt and pepper.
Dampen your hands to form the mixture into four flat burgers, cover with foil and leave to rest for 30 minutes. Wash the peppers and pat dry. To prepare the garnish, halve the peppers, remove the seeds and the white membrane. Lay them on a baking sheet, cut side down and roast them under a hot grill until the skin blisters and darkens. Remove them from under the grill, put them in a plastic freezer bag and leave to cool. Peel them and cut them into strips.
Wash the tomatoes, remove the stalks and slice them. Peel the onion and cut it into rings. Wash the cucumber, pat dry and slice. Heat a grill pan over a high heat. Halve the buns and toast them in the pan, cut side down, for 30 seconds. Remove them from the pan. Heat some oil in the pan and fry the burgers for about 3 minutes on each side.
Spread the lower half of each bun with chilli sauce. Lay the cucumber and pepper on top and then the burgers. Place slices of tomato and onion on the burgers and sprinkle with parsley. Lay the top half of the bun on top and press down gently.