Peel the onions, cut them into slices and sauté in a pan with 1 tablespoon of extra virgin olive oil. Blend with 1/2 glass of white wine and add sugar. Close and continue cooking until soft. Mix to prevent sticking and make sure the liquid is completely. absorbed.
In the meantime, clean the broccoletti, divide them in florets and sauté in a pan with 2 tablespoons of extra virgin olive oil, salt and a pinch of chilli pepper. They’ll have to cook but stay crunchy.
Cut the hamburger buns in half and heat them on a griddle (cut part down), spread a layer of mustard beans and place the slices of provolone. If necessary, heat the cheese again so that it melts (this time with the sliced top).
Add the broccoletti, the porchetta, a layer of mayonnaise and close with the other half of bread.