Heat a large skillet over medium and add walnuts. Toast for about 4-5 minutes or until golden brown and fragrant. Occasionally shake the pan or stir nuts, watching closely so they don’t burn. Transfer to a small bowl and set aside.
Return skillet to heat and add the butter. Cook for about 3 minutes or until lightly browned and fragrant, stirring occasionally (it will smell nutty). Add pepper to taste, 1 tsp lemon juice and 15 whole sage leaves. Continue cooking about 2 minutes more, stirring occasionally.
Transfer cooked ravioli to the skillet, stirring gently to coat them in the butter. To serve, top with freshly grated Parmigiano Reggiano, walnuts and a squeeze of lemon.
