Blend the diced gorgonzola and mascarpone in a mixer, add the fresh cream. Avoid over-blending as the ingredients may separate. The cream is ready when everything is amalgamated and velvety. Set aside.

Wash the spinach well, drain and plunge into a saucepan with boiling salted water. When it comes to a boil, wash and cool under running water. Squeeze lightly and sauté in butter. Season with pepper, salt, and a grating of nutmeg. Keep warm.

Cut the fillet into slices of about 200 g each, season with salt and pepper. Heat a large pan, add a tablespoon of butter and a tablespoon of extra virgin olive oil, cook the fillet, first on one side, then on the other, for about seven minutes, until it is browned.

Arrange the spinach in the center of each plate, place the just-cooked fillet on top, cover with the slightly warmed gorgonzola sauce. Sprinkle the sauce with chopped walnuts and serve immediately.