In a pan, heat a little extra-virgin olive oil together with the garlic and the chopped parsley, then add the mussels until they open. Use Menù’s fish stock, diluting it with the liquid from the mussels and adding the amount of water needed to prepare 1070 g of fish broth, following the method indicated on the package. Add the Fiokki potato flakes and a drizzle of extra-virgin olive oil, then mix well. In the meantime, in a pan, toast the breadcrumbs in oil, flavour with the mustard pesto and add the tomatoes and chopped parsley. Stuff the open mussels with the breadcrumb mix. Transfer the creamed potatoes onto the plates and arrange the stuffed mussels on top. Garnish with freshly ground pepper, a few sprigs of wild fennel and a drizzle of extra-virgin olive oil.