For the Salsa Verde: Combine all ingredients in a bowl, tossing until thoroughly mixed.
For Assembly: Lightly toast the flatbread in oven. Smear 4 of the flatbread pieces with 1/3 cup Salsa Verde. Layer with sliced porchetta, fontina, arugula and onions. Cover with remaining flatbreqd. Press in Panini press until melted. Serve.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.