The Gnocchi is rich, creamy, and the brown butter sage sauce is the ideal showcase for beautiful, aromatic truffles. For anything involving truffles I like to look to where they are hunted: France, Spain, Italy, Australia.
This dish is a great outlet for white wine! Try Trebbiano or Vermentino from Italy, herbal, fresh, cleansing and wipes your palate clean of the rich dairy from the brown butter, wiping the slate clean and preparing you for another delicious bite. You will find similar characteristics in Albarino from Spain, all that and fresh meyer lemon zest.
Red wine your jam? There two are great choices that will not overpower the dish.
Aglianico, the flavor combination of Pinot Noir and Barolo, high acid, smooth light/medium body, flexible
Barbera, low tannins but high acid, perfect with the lemon within the gnocchi themselves and the lemon juice
added to our sauce