This recipe was inspired by Maria Luisa Scolastra from Villa Roncalli (her book at page 358). My experience with recipes from Villa Roncalli; they don't work, also this one did not produce a sauce with the quantities indicated.
But it is a memorable dish.
Very important is not to overcook the fillet as it is mostly to lean ad gets dry. If you really want it well done, put stripes of lard into it. Guanciale, Rosemary, wild fennel; Timo, garlic, laurel, Maria Luisa is always generous with spices. I will next time try to limit the variety :-) But I like the "bacche di Ginepre. There is the need of a generous amount of white wine to produce a sauce. But it is true: the guanciale with the herbs mixture smells heavenly and gives taste to the fillet
Wonderful idea to mix potato mash with greens. The original recipe was asking for savoy cabbage. I had Cime di rapa, maybe even better. To the olive oil I added butter and even a bit of spicy lard creme, but no Milk!! The necessary liquid for the mash comes from the veggies. Garlic, sage and pepper
The original Book recipe asked for the Scacciadiavoli Sagrantino as a wine and I willingly followed the advice. What can go wrong with a 2010 Sagrantino from Pambufetti? But any great red wine will accompany this dish!